#!/bin/csh -f
#+
# driftscan -- acquire image while drifting target across the slit
#
# Purpose:
#	Starting with sidereal tracking with objects centered on slits,
#	offset the telescope and begin tracking at a non-sidereal rate
#	while acquiring an exposure.  At the end of the exposure, return 
#	telescope to starting position and restore sidereal track rates.
#
# Usage:
#	driftscan [-v] <length>
# 
# Arguments:
#	-v     = verbose mode
#	length = length of drift scan [arcsec]
# 
# Output:
# 
# Restrictions:
#	- Slit must be oriented N/S so that drift scanning is purely E/W.
#	- Guide star should be at least 0.5*length arcsec from edge of pickoff mirror
#	so that it is not lost during offset
# 
# Exit values:
#	 0 = normal completion
#	 1 = wrong number of arguments
#
# Example:
#	1) Acquire a spectrum while tracking at a non-sidereal rate
#	over a 10 arcsec length:
#		driftscan 10
#
#-
# Modification history:
#	2008-Oct-23	GDW	Original version
#	2008-Oct-25	GDW	Redo logic at end; issue a telescope move
#				instead of using "west" command to return
#				to original position
#	2013-Mar-10	GDW	Add check for the slit angle being N/S
#-----------------------------------------------------------------------

set cmd = `basename $0`
set usage = "Usage: $cmd length"
set debug = 0
set wordy = 0
set format = "%12s = %s %s\n"

# parse flags...
while ( $#argv > 0 )

  # check for verbose flag...
  if ( "$1" =~ \-v* ) then
    set wordy = 1
    shift
    continue
  endif

  # exit flag check if no flags remain...
  break

end

# verify args...
if ( $#argv != 1 ) then
  printf "$usage\n\a"
  exit 1
endif

# parse args...
if ( $#argv > 0 ) then
    set length = $1
    shift
endif

cat <<EOF
------------------------------------------------------------------------
                          DEIMOS Driftscan Script
------------------------------------------------------------------------

EOF

# verify that the skypa is in the correct range...
set buf = `skypa`
set buf2 = `calc "nint($buf)"`
set skypa = `calc $buf2 + 720 % 360`
if ( $skypa != 0 && $skypa != 180 && $skypa != 360 ) then
    set default = n
    printf "\aWARNING: This script was only designed to work at a slit angle of 0 or 180,\nbut slit angle is currently $skypa.  Continue anyway? (y/n) [$default]: "
    set ans = "$<"
    if ( "$ans" == "" ) then
	set ans = $default
    endif
    set ans = `tolower $ans`
    if ( "$ans" == "y" ) then
	printf "OK, continuing despite incorrect slit angle...\n"
    else
	printf "Aborted by observer request!\n\a"
	exit 1
    endif
endif

# determine telescope offset (half the drift length)...
set offset = `calc 0.5 \* $length`

# determine tracking rate...
set ttime = `tint`

# get initial position...
set ra0 = `show -s dcs -terse ra`
set dec0 = `show -s dcs -terse dec`

# get dec (in radians)...
set dec = `show -s dcs -binary -terse dec`

# convert arcsec to seconds of time (with correction for dec)...
set nsec = `calc "$length / 15. / cos($dec)"`

# compute the rate, which is in units of [arcsec/ sec / 15]
set rate = `calc "$length/$ttime/15."`

# give feedback...
if ( $wordy ) then
    printf "Parameters:\n"
    printf "$format" length $length arcsec
    printf "$format" offset $offset arcsec
    printf "$format" ttime $ttime sec
    printf "$format" nsec $nsec "seconds of time"
    printf "$format" rate $rate sec/sec

    # check RA/DEC
    printf "\nPosition before initial offset:\n"
    printf "$format" RA $ra0 hours
    printf "$format" Dec $dec0 deg
    printf "\n"
endif

if ( $debug ) exit

# save position...
printf "Marking starting telescope position.\n"
markbase

# make offset...
printf "Offsetting telescope by $offset arcsec WEST.\n"
west $offset

if ( $wordy ) then
    # check RA/DEC
    set ra = `show -s dcs -terse ra`
    set dec = `show -s dcs -terse dec`
    printf "\nPosition at start of exposure:\n"
    printf "$format" RA $ra hours
    printf "$format" Dec $dec deg
    printf "\n"
endif

# from here on we need to be careful to clean up keywords if we exit...
onintr reset

# start exposure...
printf "Starting exposure..."
goi >& /dev/null &
waitfor -s deiccd exposip=t
printf "now exposing.\n"

# begin NS tracking...
printf "Changing to non-sidereal RA track rate.\n"
modify -s dcs dra = $rate
modify -s dcs ddec = 0.
modify -s dcs dtrack = 1

if ( $wordy ) then
    printf "Verifying non-sidereal tracking.\n"
    show -s dcs dra ddec dtrack
endif

printf "Waiting for exposure to complete.\n"
waitfor -s deiccd exposip=f

# check RA/DEC
if ( $wordy ) then
    set ra = `show -s dcs -terse ra`
    set dec = `show -s dcs -terse dec`
    printf "\nPosition at end of exposure:\n"
    printf "$format" RA $ra hours
    printf "$format" Dec $dec deg
    printf "\n"
endif

reset:

# rest tracking to sidereal rates...
printf "Restoring sideral tracking.\n"
modify -s dcs dra = 0.
modify -s dcs ddec = 0.
modify -s dcs dtrack = 0

printf "Returning telescope to starting position.\n"
set ra = `sex2dec $ra0`
set dec = `sex2dec $dec0`
modify -s dcs targra=$ra targdec=$dec movetel=1

# check RA/DEC
if ( $wordy ) then
    set ra = `show -s dcs -terse ra`
    set dec = `show -s dcs -terse dec`
    printf "\nPosition after final offset completed:\n"
    printf "$format" RA $ra hours
    printf "$format" Dec $dec deg
    printf "\n"
endif

printf "Waiting for readout to complete.\n"
wait
printf "Done!\n"
beep
exit