LWS Recommended Instrument Settings

LWS
Recommended Instrument Settings

The choice of instrument parameters is driven primarily by the observing mode in use. Below we list recommended parameters for various observing modes.

**XCALCTOOL Settings for Various Observing Modes**
Parameter	Units	Mode
Parameter	Units	Video	Imaging	LRES 10 µm	HRES 10 µm	HRES 20 µm
obsmode		chop	chop-nod	chop-nod	chop-nod	chop-nod
frmtime	s	see table	see table	0.1	0.4	0.4
savefreq	Hz	0.5	0.001	0.001	0.001	0.001
objtime	s	5	see table	see table	see table	see table
chpfreq	Hz	5	5	2.5	0.6	0.6
chpdelay	s	0.001	0.001	0.001	0.001	0.001
nodtime	s	--	30	30	30	30
noddelay	s	--	4	4	4	4

**Instrument Settings**
Parameter	Mode
Parameter	Video	Imaging 10 µm	Imaging 20 µm	LRES 10 µm	HRES 10 µm	HRES 20 µm
ZnSe Window	in	in	out¹	in	in	out¹
Sector wheel	homed	homed	homed	homed	homed	homed
Aperture Wheel	open	open	open	slit	slit	slit
Filter Wheel	11.7	(varies)	(varies)	Nwide	Nwide	Spec20
Grating	mirror	mirror	mirror	LRES²	HRES²	HRES²

Notes:

In order to prevent damage to the hygroscopic KBr dewar window, observers are required to leave the ZnSe window IN if the difference between the outside temperature and dewpoint is less than 10°C. To improve the S/N at and above 20 µm, observers may remove the window when the outside temperature is more than 10°C above dewpoint.
Observer must also specify central wavelength (cenlam) via the XLWS GUI in order to set the spectral range.

**Machine Parameters for Imaging in Various Filters**
Keyword	Filter
Keyword	L	M	7.9	8.9	9.9	Q new	11.7	12.5	17.9	18.7
frmtime [s]	0.10	0.10	0.01	0.20	0.01	0.02	0.02	0.02	0.01	0.04
frmsettl	1	1	1	1	1	1	1	1	1	1
frmcoadd	1	1	9	1	9	4	4	4	9	2
chpcoadd	5	5	10	3	10	10	10	10	10	8
fstretch [µs]	90,000	90,000	0	190,000	0	10,000	10,000	10,000	0	30,000
gain	High	High	High	High	High	High	High	High	Low	High

**OBJTIME Settings for Imaging and Spectroscopy**
Filter	Flux [Jy]
Filter	100	10	1	0.1	0.01	0.001
L,M	??	??	??	??	??	??
8-12	??	??	??	??	??	??
17-26	??	??	??	??	??	??
LRES 10µm	??	??	??	??	??	??
HRES 10µm	??	??	??	??	??	??
HRES 20µm	??	??	??	??	??	??

Note:

Imaging values will yield S/N=10 to the first Airy minimum.
Spectroscopy values will yield S/N=1 per resolution element.

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Last modified: Wed Aug 18 15:12:15 HST 1999