Cookbook for MIPS-917: 24micron Routine Photometry Flatfield

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 Photometry Flatfield

Description

We will obtain IOC acceptable routine 24um PHOTOMETRY mode flatfields (this task is repeated a number of times in different IOC campaigns) to be used on a regular basis. This activity is a companion to the 24 um routine SCAN flatfield task (MIPS-914). 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-914 will determine whether routine flatfields will be obtained in photometry or scan mode.

This task is executed in:

    MIPS Campaign D2 (twice)
    MIPS Campaign E (twice)
    MIPS Campaign F
    MIPS Campaign G
    MIPS Campaign H (twice)
    MIPS Campaign I
    MIPS Campaign J
    MIPS Campaign K

Data Collected

A 4 point dither map (1 cycle) will be obtained at 24microns with 3 second DCEs in a region of the sky chosen to avoid bright point sources. The offsets between positions are 400 arcseconds. At each position of the dither pattern there will be 14 images, so a total of 56 images will be obtained each time the task is executed. The map will require about 10.3 minutes of observing time. This is the AOR file overlaid on the sky:

HEADER: FILE_VERSION=6.1, STATUS = PROPOSAL

      AOT_TYPE:  MIPS Photometry
     AOR_LABEL:  MIPS-917-Jan29-Mar13
    AOR_STATUS:  new

 MOVING_TARGET:  NO
   TARGET_TYPE:  FIXED CLUSTER - OFFSETS
   TARGET_NAME:  MIPS-917-Jan29-Mar13
  COORD_SYSTEM:  Equatorial  J2000
     POSITION1:  RA_LON=4h47m36.70s,  DEC_LAT=+2d14m08.6s
     OFFSET_P2:  EAST_ARRAY_V=400.0",   NORTH_ARRAY_W=0.0"
     OFFSET_P3:  EAST_ARRAY_V=400.0",   NORTH_ARRAY_W=400.0"
     OFFSET_P4:  EAST_ARRAY_V=0.0",     NORTH_ARRAY_W=400.0"
OFFSETS_IN_ARRAY:  NO
OBSERVE_OFFSETS_ONLY:  NO

OBJECT_AVOIDANCE:  EARTH = YES, OTHERS = YES
    MICRON_24: FIELD_SIZE = SMALL, EXPOSURE_TIME = 3, N_CYCLES = 1
SPECIAL_OVERHEAD: IMPACT = none, LATE_EPHEMERIS = NO
RESOURCE_EST: TOTAL_DURATION=633.0257, SLEW_TIME=52.8, SETTLE_TIME=48.02568, SLE
W_OVERHEAD=180.0, SPECIAL_OVERHEAD=0.0, UPLINK_VOLUME=1819, DOWNLINK_VOLUME=4164
544, VERSION=S6.1.2
INTEGRATION_TIME: MIPS_24=48.234497,MIPS_70=0.0,MIPS_160=0.0

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

CAID and title of Precedent Task #1 (or None)
etc.

Calibration Dependencies

Dark

Output and Deliverable Products

24 micron mosaic of the observed region. This may be useful for IRS to select their flatfield regions.

24micron flatfield obtained in PHOTOMETRY 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-914 task (Routine Scan 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 the dark subtraction, among other things.
Produce a mosaic of the observed region using MIPS_ENHANCER to check for bright sources.
Median combine 56 images (with some rejection algorithm) 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 (NEED TO DETERMINE IOC TASKS ADEQUATE FOR THIS)
Aperture photometry on star using the IRAF "phot" task to measure flux
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 J. Stansberry simulations; NEED TO ADD LINK TO FLATFIELD MODEL WEBPAGE). NOTE: According to John's simulations we will need approximately 100 DCEs to get an accuracy of 0.2% (rms, over the whole array).

Once MIPS-914 is executed, we will carry out a detailed comparison between flatfields created in photometry and scan modes.

Software Requirements

DAT
IDL
IRAF

Actions Following Analysis

If S/N and quality of the fialfield requirements are met, it will be put in the calibration data archive for general use.

Failure Modes and Responses

If region of the sky used is saturated, this region will be removed from the list of flatfield regions (Jeonghee Rho's list of flatfield regions). This task is repeated a number of times with different regions of the sky, so it should be possible to obtain 24micron flatfields. If regions used are all saturated, we will look for different regions of the sky.