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MIPS : AOT Description |
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The MIPS AOT inputs are relatively few, and designing a typical MIPS
observation is not complicated. However, the design of all MIPS
observations should be based on a careful examination of the far-infrared
properties of the particular region of the sky to be observed, and a good
understanding of MIPS operation, capabilities, and limitations. In
addition, the orientation and rotation of the Spitzer focal plane can be
a factor, as can the three-hour limit of a MIPS AOR (e.g., for large scan
maps). There are four major operational modes (or Astronomical Observing Templates; AOTs) of the MIPS instrument:
Scan Map ModeThe scan map mode is designed to provide efficient mapping of large areas on the sky. A ramp motion of the scan mirror compensates for continuous telescope scanning motion, freezing the images on the arrays. The scan map mode avoids having to repoint and stabilize the telescope between exposures.
(a) Only 1/2 of map region covered by 160 micron pixels at the fast scan rate in one scan leg. Scan leg offset lookup table - how wide is half the array? What are the rest of the available offsets in units of array widths? Observers should step by at most 2.5 arcmin (1/2 array) cross-scan steps to ensure full coverage at 70 microns. Depending on the scan rate, observers might want to step by at most 1.3 arcmin (1/4 array) steps to ensure full coverage at 160. Use Spot to visualize your observations to be sure that it is doing what you think it should be doing.
Photometry and Super-Res Summary
(a) Two values indicate # of frames on-source/off-source (b) For 3 and 10 second exposure times (and 30 seconds at 24 microns) respectively. Times are per pixel on a given sky position in MIPS seconds. Actual exposure times are 1.05 times longer. (c) At 24 microns, 2 additional frames are taken per AOR, so total integration time will be longer than shown here by (2 times the exposure time). See also next note. (d) For the first cycle in an observation at 24 microns, exposure time is 1 second shorter than shown in this table. See also previous note. (e) The 10 160 micron frames combine to provide a 2' x >5' filled field of view containing 2 images of the source. (f) The 10 160 micron frames combine to provide a 4' x 5' filled field of view containing a single image of the source. (g) The 3 x 10 160 micron frames combine to provide a 2' x >5' filled field of view containing 6 images of the source sampled at sub-pixel shifts. Experienced MIPS observers might note that the 70 and 160 micron portions of the PH/SR AOT were changed with respect to our pre-launch plans to keep the source on only one side of the respective arrays. Additional images were included in the 160 micron AOT to ensure full coverage. Always use Spot to visualize your observations to be sure that it is doing what you think it should be doing.
Spectral Energy Distribution ModeThe Spectral Energy Distribution (SED) mode applies only to the 70 micron Ge:Ga array, since it requires an offset of the scan mirror that deflects light away from the optical trains for the other arrays. This operating mode provides low-resolution (R ~ 20) spectral information from about 55-96 microns. The SED optical train illuminates a slit approximately 24 pixels long on the array by 2 pixels wide, with dispersion via a reflection grating.
Total Power ModeMIPS is optimized to provide calibrated images of sources that are small enough that they can be chopped on and off of the arrays, particularly at 70 and 160 microns. The Total Power mode AOT provides a way to accurately measure extended emission as well, by chopping between an internal dark position and the sky.
Examples of MIPS AOTsSee also the Observation Planning Cookbook.
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help@spitzer.caltech.edu http://ssc.spitzer.caltech.edu/mips/aotintro.html
