MIPS : Spectral Response

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The spectral response of the MIPS arrays is given in detail in the SOM. Blocking of UV through near-IR wavelengths is such that for any source which does not grossly saturate the detectors, no measurable flux will pass through the blocking filter. Blocking will be verified on-orbit by observing the point-source modulation transfer function of the Spitzer+MIPS optics, and verifying that only terms corresponding to wavelengths within the spectral bandpasses are present. A detailed tracing of the SED mode spectral response will be provided at a later date.

During IOC/SV, 160 micron signals from K stars were detected to be about a factor of five stronger than expected. Review of the instrument design revealed a weakness in the stray light control that results in a short-wavelength (1-1.6 micron) light leak in this band; see section 8.1.3.6.6 in the SOM.

Linked here are an MS Excel spreadsheet and space-delimited text listings in table form of the the spectral response for the three MIPS imaging bandpasses. For details and a full explanation, see the MIPS chapter of the Spitzer Observer's Manual.

Excel: MIPSfiltsumm.xls. (Retrieval of this file might be dependent on the platform, software and version used. Requests for this file are possible through the Spitzer help desk.)
Text: MIPSfiltsumm.txt

The spectral response of MIPS in the SED mode was determined pre-flight using test filters and a far-IR blackbody source. The slit for the Spectral Energy Distribution (SED) mode is 2 pixels wide and 24 pixels long; however, 8 of those 24 pixels fall on side B (the noisy side) of the array. Moreover, another 4 pixels have incomplete spectral coverage due to the bad readout on side A. The resulting slit length giving complete spectral coverage is thus 12 pixels. The grating disperses the light parallel to the direction of motion of the scan mirror; CSMM motions are used to switch between object and sky positions, while spacecraft pointing is used to move the object between positions in the slit. The spectrum is dispersed by a reflection grating across 32 pixels, and covers the wavelength range from 55 to 95 microns, giving a nominal dispersion per pixel-pair of 3.4 microns. The resultant spectral resolution,lambda/delta lambda, is 15 at 52 microns, about 24 at 80 microns, and about 25 from 85 microns to the long wavelength cutoff. Basic parameters of interest for SED observations with MIPS are summarized in the SOM.

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