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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.
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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