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Principal: Almudena Alonso
Deputy: Susan Stolovy
Data Monkey(s): Almudena Alonso, Casey Papovich, Susan Stolovy
Priority:
Downlink Priority: Normal
Analysis Time: 24-48 hours
Last Updated:

Objective

To obtain a 24micron Routine Scan Flatfield

Description

We will obtain IOC acceptable routine 24um SCAN mode flatfields (this task is repeated a number of times in different campaigns) to be used on a regular basis. This activity is a companion to the 24 um routine PHOTOMETRY flatfield task (MIPS-917). The pair of activities will allow us to determine the relative efficiency and quality of flatfields created using scan and photometry AORs.

Since this task is repeated a number of times during IOC, we will observe different regions of the sky each time. The task will check for possible variations of quality of flatfield or saturation. This task will also be useful for screening regions of the sky to obtain flatfields in SIRTF routine operations. This task together with MIPS-917 will determine whether routine flatfields will be obtained in photometry or scan mode.

NOTE: 70 and 160micron scan maps will also be observed. We will determine whether different regions of the sky are suitable for obtaining flatfields/IC at all three wavelengths. If that is the case, then MIPS-915 and MIPS-916 will be redundant.

This task is executed in:

    MIPS Campaign I
    MIPS Campaign J
    MIPS Campaign K
    MIPS Campaign O
    MIPS Campaign P
    MIPS Campaign R
    MIPS Campaign V
    MIPS Campaign W

Data Collected

A 2 degree long (1 leg) scan map will be obtained using the fast scan AOT in a region of the sky chosen to avoid bright point sources. This will produce a total of 118 images to be median combined to produce a 24 um flat. The map will require about 12.7 minutes of observing time.



#  Please edit this file with care to maintain the
#  correct format so that SPOT can still read it.
#  Generated by SPOT on:  8/15/2002     11:57:42

HEADER: FILE_VERSION=6.1, STATUS = PROPOSAL

      AOT_TYPE:  MIPS Scan Map
     AOR_LABEL:  MIPS-914-Feb10-Mar25
    AOR_STATUS:  new

 MOVING_TARGET:  NO
   TARGET_TYPE:  FIXED SINGLE
   TARGET_NAME:  MIPS-914-Feb10-Mar25
  COORD_SYSTEM:  Equatorial  J2000
      POSITION:  RA_LON=5h31m20.7928s,  DEC_LAT=+03d15m00.6242s
OBJECT_AVOIDANCE:  EARTH = YES, OTHERS = YES

    REQUIRE_160: YES
      SCAN_RATE: fast
 FAST_RESET_160: NO
      STEP_SIZE: TURNAROUND=35", FORWARD=35"
    N_SCAN_LEGS: 1
   N_MAP_CYCLES: 1
SCAN_LEG_LENGTH: 2.0
MAP_CENTER_OFFSET: CROSS_SCAN = 0, IN_SCAN = 0
SPECIAL_OVERHEAD: IMPACT = none, LATE_EPHEMERIS = NO
RESOURCE_EST: TOTAL_DURATION=762.52203, SLEW_TIME=3.0, SETTLE_TIME=5.222016, SLE
W_OVERHEAD=180.0, SPECIAL_OVERHEAD=0.0, UPLINK_VOLUME=653, DOWNLINK_VOLUME=94352
95, VERSION=S6.1.2
INTEGRATION_TIME: MIPS_24=15.7,MIPS_70=15.7,MIPS_160=3.1

COMMENT_START: 

COMMENT_END:

Data Reformatting Requirements

Array Data Desired:

All Arrays

Data Reformatting Option:

NORMAL

1 FITS file per AOR per array.

Special Instructions:

Task Dependencies

MIPS-326: 24 um Scan AOT Validation - preliminary
etc.

Calibration Dependencies

Dark

Output and Deliverable Products

Mosaic of the observed region. This may be useful for IRS to select their own flatfield regions.

24micron flatfield obtained in SCAN mode.

A star observed at a grid of positions across the array will be flatfield to check the quality of the flatfield. We will provide an array map showing the location dependences -if any- of the photometric sensitivity.

Once the MIPS-917 task (Routine Photometry Flatfield at 24micron) is executed, we will provide a detailed comparison between flatfields obtained in Photometry and Scan modes at 24micron.

Data Analysis

Standard Pipeline reduction using the DAT and/or SSC Pipeline. If using the DAT, we will run MIPS_SLOPER to do subtract the dark, among other things.
Produce a mosaics of the observed region using MIPS_ENHANCER. This will be used to look for bright sources and/or saturated regions.
Median combine 118 images obtained at 24micron (with some rejection algorithm, e.g., 3sigma rejection) using the IRAF "imcombine" task to create a flatfield. Alternatively, once the flatfield DCEs are screened for possible saturation, etc, we can use the MIPS_ENHANCER to create the flatfield frame using an appropriate rejection algorithm.
Flatfield star observations at different positions across the array. We can use observations of the Focal Plane Survey: MIPS-130 and MIPS-131.
Aperture photometry on star using the IRAF "phot" task to measure flux. We will use the tasks: photpars, fitskypars to set up the photometry parameters (aperture, sky/background estimate).
Comparison of star aperture photometry at different positions across the array to determine flatfield accuracy.
Once the task is executed more than once:

we can look for possible flatfield variations with time/region of sky used
we can determine the number of DCEs necessary to construct a 'super' flatfield (see A. Alonso's report on flatfield/IC simlations; NEED TO ADD LINK TO FLATFIELD MODEL WEBPAGE). NOTE: According to our flatfield simulations we will need approximately > 60DCEs at 24 microns (depending on the zodi brightness) to get a flatfield with an accuracy of 0.2% (rms, over the whole array).

Once both this task and MIPS-917 are executed, we will carry out a detailed comparison between flatfields created in photometry and scan modes.
We will analyze the 70 and 160micron images in a similar fashion to determine if the observed region of the sky is suitable to create flatfield/ICs at all three wavelengths.

Software Requirements

DAT
IRAF
IDL

Actions Following Analysis

If the flatfield S/N and quality requirements are met, then the flatfield frame will be put in the calibration data archive.

If we find a sufficiently high number of regions of the sky good to create flatfields/ICs at all three wavelengths, we will only need to observe MIPS-914. MIPS-915 and MIPS-916 can be replaced with other plug-and-play tasks during IOC.

Failure Modes and Responses

If region of the sky used is saturated at one or more wavelengths, this region will be removed from the list of flatfield regions (Jeonghee Rho's list of flatfield regions), as ideally we would like to use the same region of the sky to obtain flatfields and ICs at all three wavelengths. If such region does not exist, then we will have to keep MIPS-914, MIPS-915 and MIPS-916 and choose the appropriate region of the sky for each wavelength.