GLIMPSE Survey Implementation

GLIMPSE Survey Overview

During standard Spitzer Space Telescope operations, IRAC "campaigns" lasting 10 days to two weeks will be scheduled. A fraction of these IRAC campaigns in the first year will be devoted to the GLIMPSE program. The GLIMPSE Survey will be performed in 8 "segments" of length ~15 degrees. Segments contain ~40 AORs. The nominal survey area is 10-65 deg and l=295-350 over latitudes |b|<1 deg. In practice, the longitude range may be reduced or extended at high longitudes in each quadrant in order to make best use of the 400 allocated hours, depending on the final performance and efficiency of Spitzer Space Telescope. The total integration time per position is 2 seconds. The observations will be stepped by half-frames along the long axis of the AOR. Every sky direction in the GLIMPSE region will be visited at least twice. Using the current version of SPOT (7.0), the submitted AORs require a total of 395 hours, reserving 5 hours to be used later for contingency.
Visibility Plot for GLIMPSE AORs for 08/25/2003 Spitzer Space Telescope launch:

Visibility of the Galactic plane to the Spitzer Space Telescope as a function of date and Galactic longitude is shown in the colored regions. The solid vertical lines show where and when a particular region is likely to be observed according to the current AOR schedule.

STATISTICS for GLIMPSE AORs for the 08/25/2003 Spitzer launch:





   GRAND TOTALS: 395 hrs    

   314 AORs  75980 exposures  303920 frames (excluding OSV)
    * observations have been made
      (updated 06/21/04)

      BY DATE
      Segment                 Actual/Desired         #AORs   #Exposures #Frames
                              Obs. Date
      ------------------------------------------------------------------------
      Observation Strategy Validation (OSV)
     *  G284.3 (RCW49)        2003 Dec 23             20       1648      6592
      ------------------------------------------------------------------------
                          ~2.5 months
      ------------------------------------------------------------------------
     *6 306-322 (-54 to -38)  2004 Mar 09 - 13        48      11049     44196
     *7 322-337 (-38 to -23)  2004 Mar 31 - Apr 03    38      10310     41240
     *2 025-040               2004 Apr 21 - 23        42      10362     41448
                                             totals  128      31721    126884
      ------------------------------------------------------------------------
                          ~3 months
      ------------------------------------------------------------------------
      5  295-306 (-65 to -54) 2004 Jul 19 - Jul 23    32       8100     32400

      8  337-350 (-23 to -10) 2004 Sep 05 - 07        35       8449     33796
      1  010-025              2004 Sep 29 - Oct 09    41       9752     39008
      3a 039-047              2004 Oct 09 - Oct 11    21       5188     20752
      3b 047-054              2004 Oct 11 - Oct 13    21       5309     21236
      4a 054-062              2004 Oct 26 - 28        23       5355     21420
      4b 062-065              2004 Oct 27 - 29        13       2106      8424
                                             totals  186      44259    177036

      BY LONGITUDE


      Segment (deg)           Actual/Desired        #AORs   #Exposures #Frames

                              Obs. Date
      ------------------------------------------------------------------------

      1  010-025              2004 Sep 29 - Oct 09    41       9752     39008
     *2  025-040              2004 Apr 21 - 23        42      10362     41448
      3a 039-047              2004 Oct 09 - Oct 11    21       5188     20752
      3b 047-054              2004 Oct 11 - Oct 13    21       5309     21236
      4a 054-062              2004 Oct 26 - 28        23       5355     21420
      4b 062-065              2004 Oct 27 - 29        13       2106      8424

      5  295-306 (-65 to -54) 2004 Jul 19 - Jul 23    32       8100     32400
     *6  306-322 (-54 to -38) 2004 Mar 09 - 13        48      11049     44196
     *7  322-337 (-38 to -23) 2004 Mar 31 - Apr 03    38      10310     41240
      8  337-350 (-23 to -10) 2004 Sep 05 - 07        35       8449     33796

GLIMPSE Observation Strategy Validation

Time will be scheduled during early Spitzer Space Telescope operations to validate our observing strategy (OSV). The GLIMPSE OSV region will be chosen to sample a range of stellar densities and diffuse background levels characteristic of the inner Galactic plane.

With the Spitzer Space Telescope launch date of August 25, 2003, the GLIMPSE OSV target is RCW49, expected to be observed at the end of December 2003:

RCW49 3 color image (2MASS J, H, K)

RCW49 3 color image (2MASS J, K, MSX A)

The OSV will consist of four 1 deg x 0.17 deg AORs nearly identical to normal GLIMPSE AORs. These will be repeated with varying frame offsets (along the strip direction) and overlaps (between strips). The GLIMPSE OSV will also perform a single 2 deg x 0.17 deg AOR to allow the evaluation of the pointing reconstruction accuracy for the full half hour it takes to do a single diagonal band across the Galactic plane.
Coverage Strategy

Each region of the plane will be covered at least twice, with IRAC in mapping mode by stepping the IRAC in array coordinates by ~1/2 of a detector width. The Plane will be covered in Segments, where each segment is composed of ~40 AORs. Each AOR is an N x M IRAC map where N is 3-5 and M varies between 20 and 90. The AOR durations vary between 45 m and 120 m.
The first AOR in a segment is given a timing constraint such that it must begin between D +/- W/2 where D is the optimal date and W is the full width of the allowed execution window of the first AOR. The width of W is proportional to the rate of change of the IRAC position angle w.r.t the Galactic Plane. W must be sufficiently small that the actual execution date of the AOR is not too different from the design date in order to ensure contiguous spatial coverage of adjacent AORs. In some parts of the Plane, W is as little as 2 days where the roll angle changes most quickly. In other parts of the Plane, W may be as large as 10 days where the roll angle is nearly constant.
Subsequent AORs in a segment after the first are given follow-on constraints such that they must begin not later than F days after the preceding AOR begins. F is also driven by the rate of change of the IRAC position angle w.r.t the Galactic Plane. F must be sufficiently small to ensure that roll angle changes between adjacent AORs do not leave wedge-shaped gaps in the spatial coverage. F is typically between 3 hours in the worst parts of the Galactic Plane where the roll angles changes quickly, and as large as 15 hours in parts of the Plane where the roll angles varies slowly.
File and AOR Naming Convention

Segments contain ~40 AORs are given names that refer to the segment number, e.g. INNER_GAL1.aor is the file of AORs for segment 1, l=10 to 25. These are the 8 segment files:

INNER_GAL1.aor
INNER_GAL2.aor
INNER_GAL3.aor
INNER_GAL4.aor
INNER_GAL5.aor
INNER_GAL6.aor
INNER_GAL7.aor
INNER_GAL8.aor

AORs themselves have names like lddd.dddddSbb.bbbbb.yyymmDD where
ddd.dddd is the Galactic longitude of the center
S is the + or - sign
bb.bbbbb is the Galactic latitude
yyyymmDD is the intended year,month,day of execution

Example of an AOR:




#  Please edit this file with care to maintain the


#  correct format so that SPOT can still read it.


#  Generated by SPOT on:  6/30/2003     17:6:1



HEADER: FILE_VERSION=7.0, STATUS = PROPOSAL



      AOT_TYPE:  IRAC Mapping


     AOR_LABEL:  l010.11015-00.85826.20040930


    AOR_STATUS:  new



 MOVING_TARGET:  NO


   TARGET_TYPE:  FIXED SINGLE


   TARGET_NAME:  10.11015GLIMPSE


  COORD_SYSTEM:  Galactic  


      POSITION:  RA_LON=10.11015d,  DEC_LAT=-0.85826d


OBJECT_AVOIDANCE:  EARTH = YES, OTHERS = YES



          READOUT_MODE: FULL_ARRAY


                 ARRAY: 3.6_5.8u=YES, 4.5_8.0u=YES


            HI_DYNAMIC: NO


            FRAME_TIME: 2.0


        DITHER_PATTERN: TYPE=none


 N_FRAMES_PER_POINTING: 1


MAP: TYPE=RECTANGULAR, ROWS=3, COLS=14, ROW_STEP=292.8, COL_STEP=139.2, 


     ORIENT=ARRAY, ROW_OFFSET=0.0,COL_OFFSET=0.0,N_CYCLE=1


SPECIAL: IMPACT = none, LATE_EPHEMERIS = NO,SECOND_LOOK = NO


TIMING1:  START_DATE=2004 Sep 30, START_TIME=00:11:01, END_DATE=2004 Oct 10, END_TIME=00:00:00






COMMENT_START: 


This is the first AOR of the GLIMPSE aor for Galactic Plane region near l= 10.11015, 


b= -0.85826 to be conducted during indicated date range


COMMENT_END:

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updated 06-21-04

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