Contents
The present document describes the LWS keyword library and
implicitly all of the functionality of the LWS instrument. In
addition to describing the internal control of the LWS
instrument, it also describes the manner in which the LWS team
expects to be able to control (or interact with) all of the
external interfaces, DCS, telescope chopper, IRE electronics,
etc.
In order for the LWS interface to look as uniform as possible
with existing Keck software, we will make the LWS/IRE keyword
interface part of the KTL keyword library and support KTL
show, modify, and xshow commands. This design is essentially
as described in Keck Software Document 45: LWS Host
Software Design (Lupton, 1994). Also,
BCE will be using qckMon calls to implement the
Collect-Structure interface and these qckMon calls use a
keyword-like structure so that mapping KTL keywords onto the
qckMon software will be relatively straight forward.
Hence to be specific, the LWS can be run exclusively through
its keywords using show and modify
commands (e.g., show -service lws graraw, to show
the raw motor position of the grating motor). In each of
these cases, BCE supplies an RPC server and the LWS team
supplies the KTL to RPC client-side translation layer. For
the data acquisition software, BCE hasl written a data
acquisition server that uses qckMon calls to access the
Timing Generator and Co-Adder programs and the LWS project
has written a data acquisition control program that uses KTL
keywords to communicate to the BCE data acquisition RPC
server. The current document describes the LWS/IRE
keywords.
Before going on to describe each of the keywords in detail,
we would like to point out that there are two distinct types
of keywords in the LWS keyword library. There are the so
called "normal" keywords and there are the
"cached" keywords. The cached keywords are for
informational purposes only. In other words, setting the
values of cached keyword causes no change in the status of
the LWS instrument. An example of a cached keyword is
objname (object name) or photondc (photon duty cycle).
The values of these keywords are simply stored for
informational purposes, perhaps to be written to a data file
or to be displayed on the instrument control GUI. If a
keyword is a cached keyword, this is indicated in the first
line of the subsection describing the keyword.
- objname.a
ObjectName
string
read/write
cached
-
This keyword specifies the name of the object being observed for
recording in the data header.
Keyword values: Character string.
- outdir.a
OutputDirectory
string
read/write
normal
- This keyword specifies output directory path for the
data file.
Keyword values: Character string.
- outfile.a
OutputFile
string
read/write
normal
- This keyword specifies the name of the output data file.
Keyword values: Character string.
- frameno.a
FrameIndexNumber
string
read/write
normal
- This keyword specifies the index number of the data frame.
Keyword values: Character string.
- objtime
ObjectTime
double
read/write
cached
- This keyword is used to specify the integration time
that is to be spent on the object.
Keyword values: Units of this keyword are seconds.
- exptime
ExposureTime
double
read/write
cached
- This keyword specifies the total duration of the exposure.
Keyword values: Units of this keyword are seconds.
This keyword gives the total exposure time required to
ensure the specified value of objtime taking into
account an equivalent exposure time on the sky and the
observational inefficiencies.
The fundamental apects of the LWS that need to be controlled
in a routine manner by an observer are related to controlling
the exposure time, the observing mode, and data archiving.
Since certain aspects of the detector (e.g., pixel saturation)
and chopping and nodding interact directly with each other and
the efficiency of the observation, these aspects must also be
controllable at some level by the observer. In this section
we shall define keywords directly related to issues.
The fundamental parameters that an observer will normally
control are given in the table ``Observing Parameters''. From
these fundamental parameters all of the other related LWS and
IRE keywords are derived.
Once the fundamental observing parameters are specified, all
the dependent keywords can be calculated. Also, some of the
specified values of the fundamental keywords must be reset in
order to make them consistent with integer number of detector
frames, chop cycles, and nod cycles, etc. The manner in which
the dependent keyword values are calculated depends on the
obsmode . These calculations will be described
next.
- chop-nod Mode:
-
To calculate the dependent keyword values in chop-nod
mode, traverse the following equations once. (Note:
certain fundamental keywords get recalculated. At each
step, use the most current value of each keyword.)
where the function "CEILING" means to pick the
next highest integer, and the function "ROUND"
means to pick the closest integer.
- Chop Mode:
-
- Nod Mode:
-
- Stare Mode:
-
- backrow.a
BackgroundRow
integer
read/write
normal
- This keyword indicates the central row of the 3x3 pixel
grid for the background measurement.
Keyword values: Dimensionless row number. Valid
values lie in the range [1,96].
- backcol.a
BackgroundColumn
integer
read/write
normal
- This keyword indicates the central column of the 3x3
pixel grid for the background measurement.
Keyword values:
Dimensionless column number. Valid values lie in the
range [1,96].
- backgrnd.a
Background
double
read only
normal
- This keyword indicates the fraction of full well the
detectors are running at. This keyword has its value
updated every time the coadders read out. The value
presented in average value of a 3×3 grid of adjacent pixels
in the center of the good portion of the array.
Keyword values: The value of this keyword is a
fraction in the range [0,1].
- pxlev.a
PixelLevel
double
read only
normal
-
This keyword indicates the average fraction of the ADC
range for pixel reads in the 3×3 grid of background
monitor pixels.
Keyword values: Dimensionless pixel ADC level.
Valid values lie in the range [0.0,1.0].
- rslev.a
ResetLevel
double
read only
normal
-
This keyword indicates the average fraction of the ADC
range for reset reads in the 3×3 grid of background
monitor pixels.
Keyword values: Dimensionless pixel ADC level.
Valid values lie in the range [0,4095].
- endut
EndUT
string
read/write
cached
- This read-only keyword indicates the ending time of the
current exposure in UT.
Keyword values: The output units are time expressed
as an ASCII string; e.g., hh:mm:ss.
- obsmode
ObservationMode
string
read/write
normal
- This keyword specifies the observing mode.
Keyword values:
- chop-nod = chop-nod mode
- chop = chop mode
- nod = nod mode
- stare = star mode
- savefreq
SaveFrequency
double
read/write
cached
-
The frequency at which data is saved to media.
Keyword values:
The dimensions of this keywords is Hz. The valid ranges
of this keywords are: ??
- chpbeams
ChopperBeams
integer
read/write
cached
-
This keyword specifies the number of chop positions
(either 1 or 2). In the LWS FITS structure, the value of
this keyword defines NAXIS3. This keyword belongs to the
LWS keyword library.
Keyword values:
- 1 = Single chop beam. Used in staring mode and
nod mode
- 2 = Double chop beam. Used in chop and chop/nod mode.
- chpdelay
ChopperDelay
double
read/write
cached
-
This keyword specifies how long the data collection
program should wait after a chop move before considering
the data to be valid. This keyword belongs to the LWS
chopper keyword library.
Keyword values:
Units: dimensionless, number of frames.
- irefreq
IREFrequency
double
read/write
cached
-
This keyword specifies the frequency at which the IRE
sends chop trigger signals to the chopping secondary
mirror. A copy of the value of this keyword should be
copied into the CARA chopper keyword library via chpfreq. This keyword belongs
to the IRE keyword library .
Keyword values:
The units of this keyword are Hz.
- nodbeams
NodBeams
integer
read/write
cached
-
This keyword indicates the number of nod positions (either
1 or 2). In the LWS FITS structure, the value of this
keyword defines NAXIS5.
Keyword values:
- 1 = Single nod beam. Used in staring and chop modes.
- 2 = Double nod beams. Used in nod and chop/nod modes.
- nodtime
NodTme
double
read/write
cached
-
This keyword specifies the time spent is a nod position;
i.e., 1/2 the nod period.
Keyword values:
The units are seconds.
- noddelay
NodDelay
double
read/write
cached
-
This keyword specifies the nominal length of time that the
LWS data collection program will wait before the nod
motion settles to its final resting position.
Keyword values:
The units are seconds.
- secmode
SectorWheelMode
string
read/write
normal
-
This keyword specifies the chopper mode.
Keyword values:
- off = chopper off
- sector = sector wheel is the source of chopping
- secondary = chopping secondary is the chopper.
- secbeam0
SectorWheelBeam0
enumerate
read/write
normal
-
The default sector wheel beam position. Sector wheel
chopping alternates between this beam position and secbeam1 . Note, these beam
positions are read into the motor controllers only when
secmode is set. So to
change these values, secmode must be set to off, then
secbeam0 and secbeam1 can be set. Then set
secmode back to sector .
Keyword values:
- open = The detector looks out unobstructed--same as
home position (secraw=0).
- mirror = The detector looks at shiny blade blade
(secraw=-67).
- transparent = The detector looks at a blackened
blade
(secraw=267).
- secbeam1
SectorWheelBeam1
enumerate
read/write
normal
-
This keyword specifies what position on the sector wheel
the detector will look at in beam position 1 (sector wheel
chopping occurs between beam position 0 and beam position
1). Note, these beam positions are read into the motor
controllers only when secmode is set. So to change
these values, secmode
must be set to off, then secbeam0 and
secbeam1 can be set. Then set secmode back to sector .
Keyword values:
The default value for this keyword is ``blocked''. Valid
values for secbeam1 are the same as for
secbeam0 --see above.
- sectellm
SectorWheelTellMotor
string
write only
normal
-
Keyword used to send an arbitrary ASCII string to the
sector wheel stepper motor.
Keyword values:
Arbitrary ASCII control string automatically prefaced by
the sector wheel motor number. Convenient strings to remember:
- ST0 turn motor controller on;
i.e., modify -service lws sectellm=ST0
- ST1 turn motor controller off.
Note: Turning motor power off and on will not reset
counter, but motor is likely to move to nearest pole.
- sechome
SectorWheelHome
Boolean
write only
normal
-
Boolean keyword to home the sector wheel stepper motor.
Keyword values:
Setting this keyword value to ``t'' mean to home the
sector wheel motor.
- secraw
SectorWheelRaw
integer
read only
normal
-
Integer keyword that reports the raw motor step position
of the sector wheel. To actually move the sector wheel,
use the keyword secdel--see below.
Keyword values: Any valid long integer value is
acceptable. One revolution of the sector wheel is 2000
steps (micro-step mode).
- secdel
SectorWheelDelta
integer
write only
normal
-
Integer keyword that allows one to change the raw motor
step position of the sector wheel. To reade the sector
wheel position, use the keyword secdel (see above).
Keyword values:
Any valid long integer value is acceptable. (See,
however, the keyword secbeam0 for valid beam
position values.
- savedc
SaveDutyCycle
double
read/write
cached
-
Save duty cycle due to the non-zero value of saveovhd.
Keyword values:
Dimensionless fraction.
- chpdc
ChopperDutyCycle
double
read/write
cached
-
This read only keyword indicates what duty cycle (or
efficiency) has been achieved by the chopper; i.e., valid
data time in each beam position divided by the total time.
This keyword belongs to the CARA chopper keyword
library .
Keyword values:
Dimensionless fraction.
- noddc
NodDutyCycle
double
read/write
cached
-
This read only keyword specifies the nod duty cycle (or
efficiency) obtained; i.e., nod data valid time divided by
the total time.
Keyword values:
Dimensionless fraction.
- photondc
PhotonDutyCycle
double
read/write
cached
-
This keyword indicates the total duty cycle (or efficiency)
of collecting photons both on and off source, including all
over-heads due to detector timing, chopper inefficiency, and
nodding inefficiency, etc.
Keyword values:
Dimensionless fraction.
- windowin
WindowIn
Boolean
read/write
normal
-
This keyword specifies whether or not the 10 µm window is in.
Keyword values:
A value of ``t'' indicates the 10 µm
window is in. A value of ``f'' indicates that the 10 µm
window is out of the beam and the LWS operating mode is
suitable for 20 µm data collection.
- wintellm
WindowTellMotor
string
write only
normal
-
Keyword used to send an arbitrary ASCII string to the window
flipper stepper motor.
Keyword values:
Arbitrary ASCII control string automatically prefaced by the
window stepper motor number.
Convient strings to remember:
- ST0 Turn motor controller on; i.e.,
modify -service lws wintellm=ST0
- ST1 Turn motor controller off.
Note:
Turning motor power off and on will not reset counter, but
motor is likely to move to nearest pole.
- apname
ApertureName
string
read/write
normal
-
Indicates name of aperture in place, or the name of the
aperture which the aperture mechanism should place in the
beam.
Keyword values:
- pixels_2 Two pixel wide slit
- pixels_4 Four pixel wide slit
- pixels_6 Six pixel wide slit
- open Wide open aperture for imaging
- home Move to home position without
slow seeking of position and re-zeroing of apraw, etc.
- dark Move to a position between aperture
openings for dark frame.
- apos
AperturePosition
integer
read/write
normal
-
Indicates the position of the aperture in units of the
aperture position number.
Keyword values: There
are 4 valid aperture positions. Current assignments of the
aperture positions are:
- 0: Home position (apname=home)
- 1: Open (apname=open)
- 2: Two pixel wide slit (apname=pixels_2)
- 3: Dark (apname=dark)
- 4: Four pixel wide silt (apname=pixels_4)
- 5: Six pixel wide slit (apname=pixels_6)
- apraw
ApertureRawSteps
integer
read/write
normal
-
Indicates the position of the aperture wheel in raw number
of steps CW from the home (apraw =0) position.
Keyword values: Valid values of apraw lie in the
range of [0, 599999]. The home position is defined to be at
apraw=0.
- apangle
ApertureAngle
double
read/write
normal
-
Indicates the position angle of the aperture wheel.
Keyword values:
Input units: degrees.
Internal units: radians. Valid input values of
apangle lie in the range of [0, 360.0). The home position
is defined to be at apangle=0.0
- aptellm
ApertureTellMotor
string
write only
normal
-
Keyword used to send an arbitrary ASCII command string to
the aperture stepper motor.
Keyword values:
Arbitrary ASCII command string automatically prefaced
with the aperture motor number.
Convient strings to remember:
- ST0 Turn motor controller on; i.e.,
modify -service lws aptellm=ST0
- ST1 Turn motor controller off.
Note: Turning motor power off and on will not reset
counter, but motor is likely to move to nearest pole.
- aphome
ApertureHome
Boolean
write only
normal
-
This keyword is used to move to the home position for the
aperture wheel and to zero apraw, apangle,
and apos. Note that before aphome can be
used, the internal home microswitch must be connected to the
motor controller. This is done by setting
msrelay=closed. After the home position is
reached, the microswitch must be disconnected for low noise
operation. This is done by setting msrelay=open.
Keyword values:
Valid values of this Boolean are ``t'' and ``f''. Note that
setting aphome=t causes a slow seek of the home
position and resetting of the values of apraw,
apos, and apangle. To move to the home
position without resetting the position counter, use
apname=home.
- filname
FilterName
string
read/write
normal
-
This keyword is used to move the filter wheel to a specified filter.
Keyword values:
There are 16 valid filter wheel positions--see filpos
description for value values.
- filpos
FilterPosition
integer
read/write
normal
-
Indicates the position of the filter wheel in units of the
16 basic viable filter positions as opposed to the current
filter name assignments.
Keyword values:
Current assignments of the filter positions to filters are:
Pos |
Name |
filraw |
Description |
0 |
Home |
0 |
Home position |
1 |
12.5 |
6000 |
OCLI Silicate ``S'' filter, 11.9 to 13.0 µm
|
2 |
11.7 |
43,500 |
OCLI Silicate ``R'' filter, 11.1 to 12.2 µm
|
3 |
10.4 |
81,000 |
OCLI Silicate ``Q'' filter, 9.7 to 10.7 µm
|
4 |
9.9 |
118,500 |
OCLI Silicate ``P'' filter, 9.3 to 10.2 µm
|
5 |
8.9 |
156,000 |
OCLI Silicate ``O'' filter, 8.3 to 9.2 µm
|
6 |
8.0 |
193,500 |
OCLI Silicate ``N'' filter, 7.5 to 8.2 µm
|
7 |
10.3 |
231,000 |
W10692, 9.8 to 10.8 µm filter
|
8 |
open |
268,500 |
OPEN |
9 |
L |
306,000 |
Standard ``L'' filter, 3.5 to 4.15 µm
|
10 |
M |
343,500 |
Standard ``M'' filter, 4.4 to 5.0 µm
|
11 |
open1 |
381,000 |
22.2 to 23.41 µm
|
12 |
17.9 |
418,500 |
16.9 to 18.9 µm
|
13 |
18.7 |
456,000 |
Q2, 18.4 to 18.9 µm
filter
|
14 |
Nwide |
493,500 |
W10527-8, 7 to 14 µm
|
15 |
spec20 |
531,000 |
6.942 µm cut-on long pass filter
|
16 |
spec10 |
568,500 |
13.712 µm cut-on long pass filter
|
- filraw
FilterRawPosition
integer
read/write
normal
-
Indicates the position of the filter wheel in raw motor
steps CW from the home (filraw=0) position.
Keyword values: Valid positions of filraw lie
in the range [0, 599999]. The home position is defined
to be filraw=0.
- filangle
FilterAngle
double
read/write
normal
-
Indicates the position angle of the filter wheel.
Keyword values:
Input units: degrees.
Internal units: radians. Valid input values of
filangle lie in the range [0, 360.0). The home position is
defined to have filangle=0.0.
- filtellm
FilterTellMotor
string
write only
normal
-
Keyword used to send an arbitrary ASCII command string to
the filter stepper motor.
Keyword values: Arbitrary ASCII command string
automatically prefaced with the filter motor number.
Convient strings to remember:
- ST0 Turn motor controller on; i.e.,
modify -service lws filtellm=ST0
- ST1 Turn motor controller off.
Note: Turning motor power off and on will not reset
counter, but motor is likely to move to nearest pole.
- filhome
-
This keyword is used to move to the home position for the
filter wheel and to zero filraw, filangle, and filpos. Note
that before filhome can be used, the internal home
microswitch must be connected to the motor controller. This
is done by setting msrelay=closed. After the home
position is reached, the microswitch must be disconnected
for low noise operation. This is done by setting
msrelay=open.
Keyword values: Valid values of this Boolean
are ``t'' and ``f''. Note that setting filhome=t causes
a slow seek of the home position and resetting of the
values of filraw, filpos, and filangle. To move to the
home position without resetting the position counter,
use filname=home.
- alphac
AlphaCenter
double
read/write
normal
-
This keyword specifies the angle between the input beam and
the input beam to detector angle; i.e., . Thus twice
alphac is the angle between the input beam and the
dector beam (beam to the center of the detector).
Keyword values:
The dimensions of this keyword are radians.
- dgamma
DGamma
double
read/write
normal
-
This keyword specifies the half angular size of the array;
i.e., .
Keyword values: The dimensions of this keyword
are radians.
- dhigh
DHigh
double
read/write
normal
-
This keyword specifies the grating groove separation, d, for
the high resolution grating.
Keyword values: The dimension of this keyword
is microns.
- dlow
DLow
double
read/write
normal
-
This keyword specifies the grating groove separation, d, for
the low resolution grating.
Keyword values: The dimension of this keyword
is microns.
- zposhigh
ZeroPositionHigh
integer
read/write
normal
-
This keyword specifies the zero offset position in motor
steps for the high resolution grating (see calculation of
grapos from other keywords; e.g., cenlam,
below).
Keyword values: This keyword is the dimensionless
number of stepper motor steps.
- zposlow
ZeroPositionLow
integer
read/write
normal
-
This keyword specifies the zero offset position in motor
steps for the low resolution grating (see, for example, the
calculation of graraw in the definition of
grapos below).
Keyword values: This keyword is the dimensionless
number of stepper motor steps.
- zposimg
ZeroPositionImaging
integer
read/write
normal
-
This keyword specifies the zero offset position in motor
steps for the imaging mirror on the mirror/grating turret.
Keyword values: This keyword is the dimensionless
number of stepper motor steps.
- graname
GratingName
string
read/write
normal
-
This keyword is use to specify any of a number of preset
positions for the grating/mirror turret mechanism.
Spectroscopic keyword name values start with ``H'' or ``L''
for high or low resolution modes. The next digit is the
order number. This is followed by a dash (i.e., ``-''), then
the set wavelength (to the nearest 1/100th of a
micron) of the grating to be placed in the center of the
detector array. (To position an arbitrary wavelength at the
start, center, or end of the array use the keywords
startlam, cenlam, endlam,
grating, and order.) Wavelengths have
been selected to cover the full spectral range of the window
with 16 pixel overlap in the 10 and 20 micron windows and 38
pixel overlap in the 5 micron window (the 5 micron window
still only requires very few settings).
Keyword values: Valid keyword values are listed
below in the accompanying tables. (Numbered entries range
from short wavelengths--low numbered entries, to
progressively longer wavelengths--larger numbered entries).
Besides the keyword values listed in the tables below,
graname can take on the value graname =
home which will move to the grating home position without
slow seeking of the home switch and re-zeroing of filraw,
etc.
The appropriate values of graraw can be calculated from
the central wavelengths of the preset filter positions by
use of the following formulae:
,
where for d the appropriate value of either dhigh or dlow must be selected and for
the appropriate value of zposhigh or zposlow must be used depending
on whether the high or low resolution gratings are used.
graname |
cenlam [µm] |
Bandpass Filter |
Imaging Mode
|
imaging |
N/A |
Low Resolution Mode
|
L3-3.50 |
3.50 |
L
|
L3-4.00 |
4.00 |
L3-4.50 |
4.50 |
M
|
L3-5.00 |
5.00 |
L3-5.50 |
5.50 |
High Resolution Mode
|
H5-3.50 |
3.50 |
L
|
H5-3.55 |
3.55 |
H5-3.60 |
3.60 |
H5-3.65 |
3.65 |
H5-3.70 |
3.70 |
H5-3.75 |
3.75 |
H5-3.80 |
3.80 |
H5-3.85 |
3.85 |
H5-3.90 |
3.90 |
H5-3.95 |
3.95 |
H5-4.00 |
4.00 |
H5-4.05 |
4.05 |
H5-4.10 |
4.10 |
H5-4.15 |
4.15 |
H3-4.53 |
4.53 |
M
|
H3-4.60 |
4.60 |
H3-4.67 |
4.67 |
H3-4.74 |
4.74 |
H3-4.80 |
4.80 |
H3-4.87 |
4.87 |
H3-4.94 |
4.94 |
H3-5.00 |
5.00 |
Low Resolution Mode
|
L1-8.00 |
8.00 |
spec10 |
L1-9.00 |
9.00 |
L1-10.00 |
10.00 |
L1-11.00 |
11.00 |
L1-12.00 |
12.00 |
L1-13.00 |
13.00 |
High Resolution Mode
|
H2-7.61 |
7.61 |
Nwide
|
H2-7.84 |
7.84 |
H2-8.06 |
8.06 |
H2-8.28 |
8.28 |
H2-8.50 |
8.50 |
H2-8.72 |
8.72 |
H2-8.94 |
8.94 |
H2-9.15 |
9.15 |
H2-9.37 |
9.37 |
H2-9.58 |
9.58 |
H2-9.79 |
9.79 |
H2-9.99 |
9.99 |
H2-10.20 |
10.20 |
H2-10.40 |
10.40 |
H2-10.61 |
10.61 |
H2-10.80 |
10.80 |
H2-11.00 |
11.00 |
H2-11.20 |
11.20 |
H2-11.39 |
11.39 |
H2-11.58 |
11.58 |
H2-11.77 |
11.77 |
H2-11.96 |
11.96 |
H2-12.14 |
12.14 |
H2-12.33 |
12.33 |
H2-12.51 |
12.51 |
H2-12.68 |
12.68 |
H2-12.86 |
12.86 |
H2-13.03 |
13.03 |
H2-13.21 |
13.21 |
H2-13.38 |
13.38 |
Low Resolution Mode
|
L1-20.00 |
20.00 |
spec20 |
High Resolution Mode
|
H1-15.23 |
15.23 |
spec20 |
H1-15.68 |
15.68 |
H1-16.13 |
16.13 |
H1-16.57 |
16.57 |
H1-17.01 |
17.01 |
H1-17.45 |
17.45 |
H1-17.88 |
17.88 |
H1-18.31 |
18.31 |
H1-18.73 |
18.73 |
H1-19.16 |
19.16 |
H1-19.58 |
19.58 |
H1-19.99 |
19.99 |
H1-20.40 |
20.40 |
H1-20.81 |
20.81 |
H1-21.21 |
21.21 |
H1-21.61 |
21.61 |
H1-22.00 |
22.00 |
H1-22.40 |
22.40 |
H1-22.78 |
22.78 |
H1-23.16 |
23.16 |
H1-23.54 |
23.54 |
H1-23.92 |
23.92 |
H1-24.29 |
24.29 |
H1-24.65 |
24.65 |
H1-25.01 |
25.01 |
H1-25.37 |
25.37 |
H1-25.72 |
25.72 |
H1-26.07 |
26.07 |
H1-26.41 |
26.41 |
H1-26.75 |
26.75 |
- graraw
GratingRawSteps
integer
read/write
normal
-
Keyword to set or report the grating position in raw motor
steps CW from the home (graraw =0) position.
Keyword values: Valid keyword values lie in the
range [0, 599999].
- grangle
GratingAngle
double
read/write
normal
-
Keyword to set or report the grating position angle.
Keyword values: Input units: degrees.
Internal units: radians. Valid keyword input values
lie in the range [0, 360.0).
- gratellm
GratingTellMotor
string
write only
normal
-
Keyword used to send an arbitrary ASCII command string to
the grating stepper motor.
Keyword values: Arbitrary ASCII command string
automatically prefaced with the grating motor number.
Convient strings to remember:
- ST0 Turn motor controller on; i.e.,
modify -service lws gratellm=ST0
- ST1 Turn motor controller off.
Note: Turning motor power off and on will not reset
counter, but motor is likely to move to nearest pole.
- grahome
GratingHome
Boolean
write only
normal
-
This keyword is used to move to the home position for the
grating wheel and to zero graraw, grangle,
and grapos. Note that before grahome can
be used, the internal home microswitch must be connected to
the motor controller. This is done by setting
msrelay =closed. After the home position is
reached, the microswitch must be disconnected for low noise
operation. This is done by setting msrelay =open.
Keyword values: Valid values of this Boolean are
``t'' and ``f''. Note that setting grahome=t causes a slow
seek of the home position and resetting of the values of
graraw, grapos, and grangle. To
move to the home position without resetting the position
counter, use graname =home.
- gradel
GratingDeltaRawSteps
integer
write only
normal
-
Keyword to move the grating by an incremental number of
steps from the current grating position. Positive value
move CW. Negative values move CCW.
Keyword values: Valid keyword values lie in the
range [0, 599999].
- cenlam CenterLambda double
read/write normal
-
This keyword specifies the wavelength to place at the center
of the detector array.
Keyword values: Any wavelength in the 5, 10, and
20 micron atmospheric windows are potential values of this
keyword.
Note: Calculation of grapos from
cenlam is as follows:
,
where for d the appropriate value of either dhigh or dlow must be selected and for
the appropriate value of zposhigh or zposlow must be used depending on
whether the high or low resolution gratings are used.
- startlam
StartLambda
double
read/write
normal
-
This keyword specifies the wavelength to place at the start
(beginning) of the detector array.
Keyword values: Any wavelength in the 5, 10, and
20 micron atmospheric windows are potential values of this
keyword.
Note: Calculation of grapos from
startlam is as follows:
,
where for d the appropriate value of either dhigh or dlow must be selected and for
the appropriate value of zposhigh or zposlow must be used depending on
whether the high or low resolution gratings are used.
- endlam
EndLambda
double
read/write
normal
-
This keyword specifies the wavelength to place at the end of
the detector array in high resolution mode.
Keyword values: Any wavelength in the 5, 10, and
20 micron atmospheric windows are potential values of this
keyword.
Note:
Calculation of grapos from endlam is as
follows:
,
where for d the appropriate value of either dhigh or dlow must be selected and for
the appropriate value of zposhigh or zposlow must be used depending on
whether the high or low resolution gratings are used.
- gramode
GratingMode
string
read/write
normal
-
This keyword specifies the grating that is being used.
Keyword values: Valid keyword values are in the
set {low, high}.
- graorder
GratingOrder
integer
read/write
normal
-
This keyword specifies the order of the grating. Note that only certain orders are useful for the LWS.
Keyword values: Any integer order number in the
set {1,2,4,6} are viable order numbers.
- gramove
GratingMove
Boolean
write only
normal
-
This keyword is used to cause the grating motor to move.
The reason there is a gramove and not equivalent
commands for the filter wheel and the aperture wheel is
because in order for a valid grating position to be
specified, several keywords may need to be specified; i.e.,
valid values for gramode,
graorder, and cenlam, and it is desirable only to
start the grating motor motion after all of these keywords
are specified.
Keyword values: A value of ``t'' causes the
grating motor to move. A value of ``f'' means that the
grating motor is not in motion.
- cenlamr
CenterLambdaReadOnly
double
read only
cached
-
Because of the order in which wavelength calculations are
made, read only versions of cenlam,
startlam, and endlam are required.
cenlamr is the read only version of
cenlam.
Keyword values: Double precision number
expressing the value of the wavelength (in microns) at the
center of the array.
- strtlamr
StartLambdaReadOnly
double
read only
cached
-
Because of the order in which wavelength calculations are
made, read only versions of cenlam,
startlam, and endlam are required.
strtlamr is the read only version of
cenlam.
Keyword values: Double precision number
expressing the value of the wavelength (in microns) at the
start of the array.
- endlamr
EndLambdaReadOnly
double
read only
cached
-
Because of the order in which wavelength calculations are
made, read only versions of cenlam,
startlam, and endlam are required.
endlamr is the read only version of
cenlam.
Keyword values: Double precision number
expressing the value of the wavelength (in microns) at the
end of the array.
- lamcov
LambdaCoverage
double
read only
cached
-
Keyword which specifies the total wavelength coverage of the
detector at the current grating setting.
Keyword values: Double precision number
expressing endlam - startlam.
- lampix
LambdaPerPixel
double
read only
cached
-
Keyword which specifies the delta lambda per pixel.
Keyword values: Double precision number
expressing ,
where 64 is the total number of good pixels in the array
along the dispersion direction.
- frmreads
FrameReads
integer
read/write
cached
-
This keyword specifies the number of frame readouts
consistent with irefreq in
chop-nod and chop modes, and with savefreq in nod and stare
modes.
Keyword values: Dimensionless number of frames to
readout and co-adding in the DSP before saving data to disk.
,
see the definitions of frmsettl and frmcoadd
below. The value of this keyword is calculated by the collect
daemon.
- frmsettl.p
FrameSettle
integer
read/write
normal
-
This specifies the number of frames in a frmreads
set discarded to allow time for the chopper to settles in
chop-nod and chop modes.
Keyword values: Dimensionless number of frames
to discard before beginning DSP co-adding.
- frmcoadd.p
FrameCoadd
integer
read/write
normal
-
This specifies the number of frmcoadd sets coadded
into DSP memory in chop-nod and chop modes for a given chop
position.
Keyword values: Dimensionless number of frames.
- chpcoadd.p
ChopCoadd
integer
read/write
normal
-
This specifies the number of frmreads sets to coadd
into DSP memory in chop-nod and chop modes before
transfering data to be saved on disk.
Keyword values: Dimensionless number of frames.
- savesets.a
SaveSets
integer
read/write
normal
-
In chop-nod or chop mode, this specifies the number of
chpcoadd sets written to
media during each nodtime;
i.e., the time spent in one nod position. In nod and stare
modes, this specifies the number of frmcoadd sets written to media
during each nodtime. In
the LWS FITS structure, the value of this keywords defines
NAXIS4.
Keyword values:
- chop-nod or chop mode: Dimensionless number of
chpcoadd sets.
- nod or stare mode: Dimensionless number of
frmcoadd
- saveovhd.a
SaveOverhead
double
read/write
cached
-
Overhead associated with transferring data from coadder
buffers to main memory.
Keyword values: The dimensions of this keyword
are seconds.
- savtmout.a
SaveTimeOut
double
read/write
normal
-
The time to wait before notifying the observer of deliquency
of the DSPs.
Keyword values: The dimensions of this keyword
are seconds. The value of this keyword should be of order
- nodsets.a
NodSets
integer
read/write
normal
-
Number of nod cycles of the telescope in a complete
observation. In the LWS FITS structure, the value of this
keyword defines NAXI6.
Keyword values: Dimensionless number of nod
cycles.
In order to understand the workings of the detector, a schematic
of the detector unit cell and all pertinent voltage and control
lines is presented in
Figure 1.
Figure 2 and
Figure 3
present the on-chip clock timing logic and timing diagrams for
the Aerojet 96×96 array.
|
Figure 1. |
|
Figure 2a. |
|
Figure 2b. |
|
Figure 3. |
The temporal relationship between the assertion of
detector reset and the enabling of the output source-followers
for each column of pixels is fixed by the gating logic of the
"L" cell. The essential points of the L-cell logic
are:
- Detector reset for the Nth
column is asserted as long as QN is
held high--the QNs are the reset
controls for their respective columns.
- The output source-follower for the Nth column cannot be enabled while
QN is held high. Consequently, the
``reset-asserted'' level can never be presented at the detector
output.
- The enabling of the output source-follower for the
Nth column requires that either the previous column
or following column has reset asserted (i.e., QN-1
or QN+1 is high).
The detector array is reset by propagating a QN
pattern through the slow shift-register. This QN
pattern is specified via the Slow-in input and clocked through
the shift-register (SR) via CKS and CK1S. Note that because
the QN logic levels are supplied by the
shift-registers, their duration (the duration of reset assert)
will be an integral multiple of the SR clock-cycle.
The QN pattern is combined with the PEAK and INIT
patterns in the L-cell to determine the detector
readout-enable sequence. Note that it is possible to specify a
readout pattern for which the array output is meaningless;
e.g., it is possible to specify a QN pattern in
combination with a PEAK and INIT pattern which enables more
than one output source-follower per readout line.
The simplest QN pattern is shown in Figure 3. This pattern consists of a
single high pulse with a duration of one SR clock-cycle. When
this pattern is propagated through the shift-register, the
array is sequentially reset, column by column, with only one
column at a time being held at the reset level. The output
source-followers are enabled in a ``legal'' fashion by
applying the indicated PEAK and INIT clock pattern. This
readout pattern will be referred to as the ``NORMAL'' mode.
In the NORMAL mode, the output source-followers for each
column are enabled twice during a frame readout. The first
enable for a particular column begins one SR clock-cycle prior
to reset being asserted for that column. The duration of the
readout-enable is half of a SR clock-cycle. The second enable
begins half a SR clock-cycle after reset is deasserted and
also has a duration of half of a SR clock-cycle. The first
readout-enable for a column is referred to as
PIXEL-read-enable or just PIXEL. The second readout-enable is
referred to as RESET-read-enable or RESET.
From Figure 3, it is clear that the
PIXEL and RESET for a given column are interlaced with the
PIXEL and RESET of nearby columns. In particular, the
PIXEL/RESET pattern for a single frame readout is given by
(P01 xxx) (P02 xxx) (P03 R01) (P04 R02) ... (P96 R94) (xxx R95) (xxx R96)
where P## represent PIXEL for column ##, R## represents RESET
for column ##, and the ``xxx'' represent a null state (i.e., no
output source-followers are driving the readout lines). The
pair groupings indicated by the parentheses show the duration of
a SR clock-cycle. RESET for a given column is shifted by two SR
clock-cycles with respect to the corresponding PIXEL. Since the
last valid column is 96, a complete frame readout requires 98 SR
clock-cycles; i.e., 96 SR clock-cycle plus an additional 2
clock-cycles in order to obtain the last two valid RESETs (R95
and R96). As an aside, note that the shift-register contains a
97
th cell (
Figure 2a) even
though there are only 96 columns in the detector array. This
97
th shift-register cell is required in order to
obtain RESET for the 96
th column. That is,
obtaining RESET for the N
th column requires that
reset be asserted for the N+1
th column (i.e.,
Q
N+1 must be high (L-cell logic)).
To summarize the NORMAL mode:
- A complete set of PIXELs and RESETs is obtained every 98
SR clock-cycles. This set is called a ``frame''. The PIXELs
and RESETs constituting this frame do not represent true
``correlated double sampling'' (CDS) pairs since the PIXELs
are obtained prior to the RESETs. These pairs are more
appropriately referred to as ``delta-reset sampling'' (DRS)
pairs. The RESETs from the previous frame, combined with the
PIXELs from the current frame, however, do represent true CDS
pairs.
- The duration of Slow-in asserted high (slowinhi )
is fixed at 1 SR clock-cycle. This implies that reset for each
column is asserted for 1 SR clock-cycle.
- The duration of PIXELs and RESETs is 1/2 a SR clock-cycle.
- The relative shift between PIXELs and RESETs is 2 SR
clock-cycles.
- A MINIMUM of 98 SR cycles must be clocked in order to
obtain RESETs corresponding to PIXELs for columns 95 and 96 as
described previously. However, clocking more than 98 SR
cycles does nothing on-chip.
- If the number of SR clock-cycles in a frame is 98, the
integration duty cycle (i.e., time between RESET and PIXEL for a
column compared to the frame time) is given by (98-1-1.5)/98 =
97.45%. The ``-1'' accounts for the duration of reset assert
(slowinhi ) and the ``-1.5'' accounts for the
duration of PIXEL itself and the duration of an interlaced
PIXEL and RESET.
- Readout of a sub-portion of the array, specified as column
1 to column lastcol, where 1
lastcol
96, requires lastcol +2 SR
clock-cycles (again with the extra two SR cycles required to
obtain obtain the RESETs corresponding to the PIXELs for the
last 2 columns, lastcol -1
and lastcol ). Before
initiating a new frame acquisition, the Slow-in pattern must
be flushed from the shift register by supplying 98-lastcol fast CKS/CK1S
clocks. These ``quick'' SR clock-cycles may be done with PEAK
and INIT held low to disable the output source-followers while
clocking through the columns to be skipped.
|
Figure 4. |
A second mode of operation has been implemented and is
referred to as the ``NDF'' mode. In this mode, the on-chip
integration duty cycle is reduced by asserting detector reset
for a period longer than one SR clock-cycle (as is done in the
NORMAL mode). The effective result obtained by reducing the
on-chip integration duty-cycle is the same as would be
obtained through the use of a Neutral Density Filter (NDF) in
the optical path (i.e., throwing photons away).
The implementation of the NDF mode is as follows:
- This Slow-in pattern must be initiated every 97 SR
clock-cycles EXACTLY. In this mode, 97 SR clock-cycles
defines a ``frame''.
- The Slow-in pattern consists of a single high pulse having
a width 1
slowinhi
95 SR clock-cycles (i.e., reset is asserted for
slowinhi SR clock-cycles). The clocks PEAK, INIT, CKS
and CK1S have the same relationship with respect to the
low-to-high transition of Slow-in (i.e., the initialization of
Slow-in), as exists for the NORMAL mode.
- The duration of PIXELs and RESETs is 1/2 a SR clock-cycle.
- The relative shifts between PIXELs and RESETs is given by
slowinhi +1.
- The time between the last RESET of one frame and the first
PIXEL of the next frame should be exactly the same as the time
between RESETs and PIXELs within a frame. (This is satisfied
to within a few percent in the current NDF mode
implementation.) Corollaries to this:
No ``quick-clocking'' of columns is permitted; i.e., every
PIXEL and RESET must be obtained.
No frame delays are permitted.
- The integration duty cycle (i.e., time between RESET and
PIXEL for a column compared to the frame time) is
(97-slowinhi -1.5)/97 = 98.45%. The
``-slowinhi '' accounts for the duration of reset
assert and the ``-1.5'' accounts for the duration of PIXEL
itself and the duration of an interlaced PIXEL and RESET.
- In a single frame, PIXELs and RESETs from columns 1 to
96-slowinhi represent DRS pairs and pixels
97-slowinhi to 96 represent CDS pairs.
The following shows the PIXEL/RESET pattern for a single frame
in the NDF mode with slowinhi=2:
(P01 R95) (P02 R96) (P03 R97) (P04 R01) (P05 R02) ...
... (P94 R91) (P95 R92) (P96 R93) (P97 R94)
Note that P97 and R97 are essentially null states in that
detector column 97 does not exist (only the shift register cell
is present which provides input to the L-cell of column 96).
In the sections below, some of the keywords have ``.''-suffixes.
These indicate to which part of the IRE the data is passed:
``.t'' indicates the Timing Generator, ``.c'' indicates the
Co-adders, and ``.a'' indicates the RPC-server and the acquire
process. The absence of a suffix indicates that only the LWS
keyword library knows about the variable.
- pxtime
PixelTime
double
read/write
cached
-
This keyword specifies the total amount of time the DSP has
to deal with a pixel value before needing to handle a new
value. It is equal to the readout pattern length plus the
PolyCom preamp/MUX switching time.
Keyword values: The unit is seconds. This time
is composed of the adcdelay time, the dspdelay, the dsplatch, and muxswoh (nominally 6)--see Figure 4; i.e.,
The value of this keyword is calculated by the collect daemon.
- muxswoh.t
MUXSwitchOverHead
integer
read only
normal
-
This keyword provides the value of the overhead in number of
instructions allowed for switching of the PolyCom MUX.
Keyword values: The unit is a machine
instruction. The nominal value 6.
- slowinhi.t
SlowInHigh
integer
read/write
normal
-
Used only in NDFMode (ndfmode=t). This keyword
indicates how many reptitions of muxptime s and muxrtime s that the SLOWINHI
clock is held high. Holding slowin high controls the
relative position of the pixel reads and reset reads. The
shift between the pixel and reset values for a given column
is slowinhi + 1 detector
clock cycles. Large values of slowinhi cause the resets to
occur just before the pixel read (since timing pattern wrap
around is enforced in the on-chip shift register), reducing
the effective integration time on the chip and causing
photons to be thrown away. A non-unity value of slowinhi would logically require
an fstretch value of 0.
In fact, in NDFMode, fstretch is ignored.
Keyword values: The valid values of slowinhi are multiples (1 to 95)
of a machine instruction time (e.g., Peak, CKS, CK1S--see Figure 3).
- pxsettle.t
PixelSettlingTime
integer
read/write
normal
-
This keyword specifies the value of the settling time for
pixel reads in the MUX frame time--see Figure 4.
Keyword values: The units are machine
instructions. The nominal value of this quantity is 25;
i.e., roughly 2.5 .
- rssettle.t
ResetSettlingTime
integer
read/write
normal
-
This keyword specifies the value of the settling time for
reset reads in the MUX frame time--see Figure 4.
Keyword values: The units are machine
instructions. The nominal value of this quantity is 25;
i.e., roughly 2.5 .
- fstretch.t
FrameStretch
integer
read/write
normal
-
This keyword is only applicable in normal timing generator
mode (ndfmode =f). This keyword specifies the idle
time for the Timing generator at the end of frame readout
clocking. It can be used to extend the detector integration
time.
Keyword values: The units are machine
instructions. The nominal value for this keyword is 0.
The value of this keyword is calculated by the collect daemon.
- fsscale.t
FrameStretchScale
integer
read only
normal
-
This keyword specifies the proportionality constant for
calculation of the frame stretch time.
Keyword values: Units are machine instructions.
- fsoh.t
FrameStretchOverhead
integer
read only
normal
-
This keyword specifies the overhead for the frame stretch in
terms of machine instructions.
Keyword values: Units are machine instructions.
- mic.a
MachineInstructionCycle
double
read only
normal
-
This keyword specifies the time for a timing generator
machine instruction cycle in units of seconds.
Keyword values: Units are seconds per machine
instruction.
- ndfmode.a
NDFMode
Boolean
read/write
normal
-
This Booleans specifies whether or not NDF mode is active.
Changing ndfmode.a requires reconfiguring the DSPs
in order to take effect.
Keyword values: Valid values for this Boolean are
``t'' and ``f''. A value of ``t'' indocates the LWS is in
NDF mode. A value of ``f'' indicates ``normal'' mode--see
detector timing overview above.
- frmtime
FrameTime
double
read/write
cached
-
This keyword contains the value of the frame time. If
frmtime is written, it should only affect
fstretch. If an unviable frmtime is
written, an error message to this effect is returned.
Keyword values: The units of this keyword are
seconds. The value of this keyword is given by:
- NORMAL mode:
- NDF mode:
where
The value of this keyword is calculated by the collect daemon.
- normfmoh.t
NormalFrameOverhead
integer
read only
normal
-
This keyword specifies the number of machine instructions
overhead at the beginning of a normal frame.
Keyword values: Nominal value = 52. It is only
used when ndfmode =``f'''.
- ndffmoh.t
NDFModeFrameOverhead
integer
read only
normal
-
This keyword specifies the number of machine instructions in
overhead at the beginning of a frame in NDF mode.
Keyword values: Nominal value = 40. It is only
used when ndfmode =``t''.
- frmdc
FrameDutyCycle
double
read only
cached
-
This keyword contains the duty cycle (or data collection
efficiency) of a single frame of data.
Keyword values: The value of this keyword is a
fraction in the range [0,1]. This keyword is the fraction
of time that data is been collected during a frame time.
The formula for this keyword is given by
where for NORMAL mode, slowinhi =1. See definition
of frmtime for definitions of muxp and
muxp. The value of this keyword is calculated by
the collect daemon.
- lastcol.a
LastColumn
integer
read/write
normal
-
This keyword specifies the number of the last detector
column for which ADC conversion and DSP data collection will
be performed. This keyword is only valid in ndfmode =f. Changing
lastcol requires reconfiguring the DSPs in order
to talk effect.
Keyword values: The units for this keyword is
column number. Typical values lie between 1 and
96; i.e., one column past the last active detector column.
- convert.t
Convert
integer
read/write
normal
-
This keyword specifies the total time (in units of
instructions) the DSP has for data capture.
Keyword values: The natural unit is a machine
instruction.
- colswoh.t
ColumnSwitchOverhead
integer
read only
normal
-
This keyword specifies the overhead in units of machine
instruction allowed for switching to a new column.
Keyword values: Dimensionless. Nominal value =
8.
- fcolswoh.t
FastColumnSwitchOverhead
integer
read only
normal
-
This keyword contains the total time for a PolyCom clock MUX
group; i.e., the time required to just clock though a column
without reading out the data.
Keyword values: The natural unit of this keyword
is seconds. The nominal value for this keyword is
corresponds to12 mic.
The timing for the capture of data in the Co-adders is given
schematically in
Figure 4. This figure
indicates the various times required for a pixel (or reset) adc
conversion, including the PolyCom preamp/MUX switching overhead
time and the DSP convert time,
convert. Included in the MUX group
time is the time required for the signals to settle (either
pxsettle or
rssettle ) which is separately
controllable for pixel slews and reset slews.
- osdac.c
OffsetDAC
integer
read/write
normal
-
This keyword specifies the value of the offset DAC ( DAC
``C'') which should be used to cancel some of the DC
operating point of the Aerojet detector.
Keyword values: The units for this keyword is DAC
numbers. The IRE DACs are 16-bit DACs, so values between 0
and 65535 are valid.
- smainput.c
SMAInput
string
read/write
normal
-
This keyword specifies which of the SMA inputs the Co-Adders
are to read the data from.
Keyword values: Units for this keyword are SMA
input number. Valid values are "SMA1",
"SMA2", "SMA3", and "SMA4".
- gain.c
CoadderGain
string
read/write
normal
-
This keyword specifies the LWS electronics gain in units of
electrons per ADC unit.
Keyword values: Valid values are and the
corresponding saturated ADC are given in the Table below.
Gain [e-/DN]
|
Full Well
(4095 ADC units)
|
38E |
1.6 × 105 |
82E |
3.6 × 105 |
117E |
5.1 × 105 |
120E |
5.2 × 105 |
160E |
7.0 × 105 |
200E |
8.7 × 105 |
240E |
1.0 × 106 |
360E |
1.6 × 106 |
400E |
1.7 × 106 |
440E |
1.9 × 106 |
480E |
2.1 × 106 |
510E |
2.2 × 106 |
560E |
2.4 × 106 |
600E |
2.6 × 106 |
- lpassfil.c
LowPassFilter
string
read/write
normal
-
This keyword specifies the computer controllable value of
the frequency foot of the input filter.
Keyword values: The units for this keyword are
kHz. Valid values are "2KHZ", "20KHZ",
"200KHZ", "2MHZ", and "OFF".
- tvmode.a
TVMode
Boolean
read/write
normal
-
This keyword specifies whether or not the data coming off
the detector is to be recorded or just displayed. TV mode
is used for setting up the detector without recording all of
the invalid data that occurs during setup.
Keyword values: The values of this Boolean are
``t'' and ``f''. A value of ``t'' indicates that TV mode is
on and active. In this case data is not recorded. A value
of ``f'' indicated that TV mode is off and data is to be
recorded.
- tiltadel
TiltMotorADelta
integer
write only
normal
-
This keyword specifies how many steps to increment or
decrement the ``A'' dewar tilt stepper motor. Note:
Positive steps turns the motor CW and increases the
gap in the LWS mounting bracket for motor A. (Motor A is a
right-handed mechanism.)
Keyword values: Valid values are positive and
negative integers.
- tiltbdel
TiltMotorBDelta
integer
write only
normal
-
This keyword specifies how many steps to increment or
decrement the ``B''dewar tilt stepper motor. Note: Positive
steps turns the motor CCW and increases the gap in
the LWS mounting bracket for motor B. (Motor B is a
left-handed mechanism.)
Keyword values: Valid values are positive and
negative integers.
- tiltaraw
TiltMotorARaw
integer
read only
normal
-
Reads the raw number of steps the ``A'' dewar tilt stepper
motor has moved from zero. Note: Note: Positive steps turns
the motor CW and increases
the gap in the LWS mounting bracket for motor A. (Motor A
is a right-handed mechanism.)
Keyword values: Valid keyword values are any
legal signed integer value.
- tiltbraw
TiltMotorBRaw
integer
read only
normal
-
Reads the raw number of steps the ``B'' dewar tilt stepper
motor has moved from zero. Note: Note: Positive steps turns
the motor CCW and increases
the gap in the LWS mounting bracket for motor B. (Motor B
is a left-handed mechanism.)
Keyword values: Valid keyword values are any
legal signed integer value.
- tiltrad
TiltRadial
integer
read/write
normal
-
This keyword tilts the dewar in the radial direction by
moving both the ``A'' and ``B'' dewar tilt motors the same
amount.
Keyword values: Valid keyword values are any
legal signed integer value. Positive values tilt the dewar
toward the axis.
- tilttang
TiltTangential
integer
read/write
normal
-
This keyword tilts the dewar in the tangential direction;
i.e., perpendicular to motions toward or away from the
telescope axis, by moving both the ``A'' and ``B'' dewar
tilt motors opposite amounts.
Keyword values: Valid keyword values are any
legal signed integer value. Positive values increment motor
``A'' and decrement ``B'', tilting the beam towards the
fliter/grating mechanism side.
- tmatellm
TiltMotorATellMotor
string
write only
normal
-
Keyword used to send an arbitrary ASCII string to the ``A''
dewar tilt motor.
Keyword values: Arbitrary ASCII control string
automatically prefaced by the ``A'' dewar tilt motor number.
Convient strings to remember:
Note: Turning motor power off and on will not reset
counter, but motor is likely to move to nearest pole.
- tmbtellm
TiltMotorBTellMotor
string
write only
normal
-
Keyword used to send an arbitrary ASCII string to the ``B''
dewar tilt motor.
Keyword values: Arbitrary ASCII control string
automatically prefaced by the ``B'' dewar tilt motor number.
Convient strings to remember:
Note: Turning motor power off and on will not reset
counter, but motor is likely to move to nearest pole.
In order to read temperatures, the breakout box microswitches
enabling the temperature feedback circuits must be thrown. This
causes additional noise in the detector. Consequently this is
done only at appropriate times; e.g., when the detector is not
being readout. The keywords
basetmpl,
lhetmpl,
decktmpl, and
dettmpl are read only keywords that
are written by the
acquire program at appropriate times
when these temperatures can be read. The appropriate display
keywords (for control GUI's) are
basetemp,
lhetemp,
decktemp, and
dettemp which report the last valid
values of
basetmpl,
lhetmpl,
decktmpl, and
dettmpl.
- basetemp
BaseTemperature
double
read only
normal
-
Keyword for reading back the temperature of the base of the
LHe optics work surface.
Keyword values: Expected value of this keyword is
roughly 5 K during operation. Valid values lie in the range
of roughly [4.2 K, 300.0 K].
- lhetfrt
LHeTemperatureFront
double
read only
normal
-
Keyword for reading back the temperature of the front of the
LHe cryogen can.
Keyword values: Expected value of this keyword is
roughly 4 K during operation. Valid values lie in the range
of roughly [4.2 K, 300.0 K].
- lhetbak
LHeTemperatureBack
double
read only
normal
-
Keyword for reading back the temperature of the back of the
LHe cryogen can.
Keyword values: Expected value of this keyword is
roughly 4 K during operation. Valid values lie in the range
of roughly [4.2 K, 300.0 K].
- decktemp
DeckTemperature
double
read only
normal
-
Keyword for reading back the temperature of the upper optics
deck.
Keyword values: Expected value of this keyword is
roughly 7 K during operation. Valid values lie in the range
of roughly [4.2 K, 300.0 K].
- dettemp
DetectorTemperature
double
read only
normal
-
Keyword for reading back the temperature of the detector.
Keyword values: Expected value of this keyword is
roughly 8 K during operation. Valid values lie in the range
of roughly [4.2K, 300.0 K].
- basetmpl
BaseTemperatureLocal
double
read only
normal
-
The keyword basetmpl reports the appropriate value of the
base of the optics plate; e.g., lower deck which is attached
directly to the LHe flask.
Keyword values: Expected values of this keyword
lie around 5 K.
- lhetmpl
BaseTemperatureLocal
double
read only
normal
-
The keyword basetmpl reports the appropriate value of the
LHe flask.
Keyword values: Expected values of this keyword
lie around 4 K.
- decktmpl
BaseTemperatureLocal
double
read only
normal
-
The keyword basetmpl reports the appropriate value of the
optics deck; i.e., the platform above the base that holds the
pre-spectrograph optics.
Keyword values: Expected values of this keyword
lie around 7 K.
- dettmpl
BaseTemperatureLocal
double
read only
normal
-
The keyword basetmpl reports the appropriate value of the
detector temperature.
Keyword values: Expected values of this keyword
lie around 8 K.
- stbias
SwitchedTempertureBias
double
read only
normal
-
Keyword for reading back the switched temperature bias
voltage; i.e., the voltage supply for the temperture resistor
network.
Keyword values: Expected value of this keyword is
roughly 5 volts.
- detbias
DetectorBias
double
read only
normal
-
This keyword reads back the detector bias volatge value.
Keyword values: Expected value of this voltage is
roughly -4.5 volts.
- vref
VoltageReference
double
read only
normal
-
This keyword reads back the reference voltage to which the
integrating node on the unit cell source follower gate is
set to upon issuing a reset command.
Keyword values: Expected value of this voltage is
roughly -2.1 volts.
- detheatr
DetectorHeater
integer
read/write
normal
-
Keyword used to read back and set the bias voltage connected
to the detector heater to maintain a constant and
predetermined detector temperature.
Keyword values: The keyword values are in DAC
units. Valid values lie in the range [0, 65535]. The value
of this keyword is automatically set to an appropriate value
given by the value of the frmtime keyword upon
filter and/or grating mode changes. Direct setting of this
keyword over rides the suggested default settings.
- msrelay
MicroswitchRelay
Boolean
read/write
normal
- This keyword specifies whether or not the internal
microswitches of the aperture, grating, and filter wheel are
connected to the outside world. These switches need to be
closed when setting the home position of these motors and open
when not needed to reduce noise introduced into the dewar.
Keyword values:
- ``t'' = relay closed, microswitches connected to motor
controller.
- ``f'' = relays open, microswitches deactivated. This
is the state for low noise operation; i.e., data
collection.
- lvlon
LevelShifterPowerOn
Boolean
read/write
normal
-
Keyword used to turn on the Level Shifter power.
Keyword values: The keyword values are ``t''
(turn power on) and ``f'' (turn power off).
- peckon
PeckPowerOn
Boolean
read/write
normal
-
Keyword used to turn on the Peck cage power.
Keyword values: The keyword values are ``t''
(power on) and ``f'' (power off).
The keywords defined below describe the LWS keyword interface to
the Keck chopping secondary mirror. Some of the keywords
defined below belong to the CARA chopper keyword library. Some
of the keywords are LWS specific although some of them may
eventually find themselves elected to the more general purpose
CARA chopper keyword library if they are found useful for other
and future IR instruments.
- chpamp
ChopperAmplitude
double
read/write
normal
-
This keyword specifies the amplitude of the chopper throw.
This keyword belongs to the CARA chopper keyword
library.
Keyword values: Input units: arcsec.
Internal units: radians.
- chpecorr
Chopper ErrorCorrection
Boolean
read/write
normal
-
This keyword specifies whether or not the chopper uses error
correction. This will always be true for the LWS. This
keyword belongs to the CARA chopper keyword
library.
Keyword values: A value of ``t'' (integer 1)
indicates that chopper error correction is on. A value of
false (integer zero) indicates that error correction is off.
- chpfreq
ChopperFrequency
double
read/write
normal
-
This keyword specifies the frequency at which the chopping
secondary mirror should chop. This keyword belongs to the
CARA chopper keyword library.
Keyword values: Input units:
Hertz. Internal units:
Hertz.
- chpon
ChopperOn
Boolean
read/write
normal
-
This Boolean keyword determines the state of the chopping
secondary mirror. This keyword belongs to the CARA
chopper keyword library.
Keyword values: A value of ``t'' (integer 1)
indicates that the chopper is ready to accept chopper
trigger commands from the IRE and that it will move to the
next beam position as soon as the IRE gives the next chopper
trigger.
- chpang
ChopperAngle
double
read/write
normal
-
This keyword specifies the chopping position angle measured
relative to the coordinate system set by the keyword
chprel2. Note that there is no equivalent
nodpa keyword since these position angles are
always assumed to be the same. This keyword belongs to the
CARA chopper keyword library. The meaning of
chppa depends on chprel2 as follows:
- chprel2 = sky Keep position angle (from N to
E) on sky fixed.
- chprel2 = el Keep position angle relative
to elevation fixed. CW is positive.
- chprel2 = inst Keep position angle relative
to instrument fixed. CW from columns to rows.
Keyword values: Input units: degrees.
Internal units: radians.
- chppos
ChopPosition
integer
read/write
normal
-
This keyword specifies the beam position and moves the
chopper to that position. This keyword belongs to the
CARA chopper keyword library. It is expected that
this keyword will be extended to support multiple beam
position chopping.
Keyword values: Valid values are -1 (home
position), 0 (``minus'' beam) or 1 (``plus'' beam).
- chppostr
chopper-post-trigger-time
double
read/write
normal
-
This keyword specifies the delay time after the chopper
trigger is received before the chopper will begin to move.
This keyword belongs to the CARA chopper keyword
library.
Keyword values: Units are double precision
seconds.
- chppretr
chopper-pre-trigger-time
double
read/write
normal
-
This keyword specifies the interval before the chopper
trigger is expected. During this period the chopper error
correction is disabled. The chopper trigger is permitted to
be asserted only during this period. This keyword belongs
to the CARA chopper keyword library.
Keyword values: Units are double precision
seconds.
- chprelto
ChopRelativeTo
string
read/write
normal
-
This keyword determines the nature of the chop (and nod)
position angle. This keyword belongs to the CARA
chopper keyword library.
Keyword values: Character string. See
chppa for their effects.
- chptrig
chopper-trigger-mode
Boolean
read/write
normal
-
This keyword allows one to set/read the current chopper
trigger mode. When in chop trigger mode the chopper moves
in response to a signal from the instrument. This keyword
belongs to the CARA chopper keyword library.
Keyword values: Integer zero is false. Integer 1
(non-zero) is true.
Notes:
- Chop trigger mode is initially disabled. It should
only be enabled when the chopper is inactive (a bug at
present allows it to take immediate effect even when
chopping).
- When chop trigger mode is enabled, CHPPRETR and
CHPPOSTR govern how early chop trigger is allowed to be
asserted and how long after chop trigger before the
chopper starts moving (at which point chop synch is
asserted).
- Chop trigger mode should work together with error
correction and the reason for CHPPOSTR is to allow error
correction to be disabled when waiting for chop trigger,
and at a time when it is expected not to be doing much.
If error correction is off, CHPPOSTR can be set to zero.
- iretrig.p
IREChopperTrigger
Boolean
read/write
normal
-
This keyword send the command to the IRE to begin sending
chopper triggers to the chopping secondard mirror or sector
wheel chopper. This keyword belongs to the IRE chopper
keyword library.
Keyword values: Integer zero is false; i.e., do
not send triggers to the chopper. Integer 1 (non-zero) is
true; i.e., begin sending chop trigger signals.
- irepostr.p
IREChopperPostTrigger
double
read/write
normal
-
This keyword specifies (for the IRE) the delay time after
the chopper trigger is received before the chopper will
begin to move. This keyword belongs to the IRE chopper
keyword library.
Keyword values: Units are double precision seconds.
- nodamp
NodAmplitude
double
read/write
normal
-
This keyword specifies the amplitude of the nod motion.
Keyword values: Input units: arcsec.
Internal units: radians.
- nodon
NoddingOn
Boolean
read/write
normal
-
This Boolean keyword indicates the status of telescope nodding.
Keyword values: A value of ``t'' indicate that
the telescope is currently in nod mode and that it will move
after the LWS collects the specified number of frames in the
current nod position. A value of ``f'' indicates that nod
mode is disabled.
- nodpos
NodPosition
integer
read/write
normal
-
This keyword specifies the nod beam position and moves the
telescope to that position.
Keyword values: Valid values are -1 (home
position), 0 (``minus'' beam) or 1 (``plus'' beam).
Go to:
LWSHomePage -
InstrumentsHomePage -
KeckHomePage
Last modified: Tue Jun 8 17:14:34 HST 1999