Contact Stansberry - "; echo " there is a problem w/ your write-up.\n"; return ; } $row = mysql_fetch_array($result); $title = $row["title"]; $princ = $row["principal"]; $deputy= $row["deputy"]; $campn0 = $row["campn0"]; $aorkeys = $row["aorkeys"]; // get real name of principal, deputies $princ = ioc_get_person($princ); $princ = $princ[0]; $deps = explode(",",$deputy); foreach ($deps as $depty) { $depty = trim($depty); $depty = ioc_get_person($depty); $depty = $depty[0]; $depty = explode(",",$depty); $depty = $depty[0]; // last names only $deplist[] = $depty; } $deplist = implode(", ", $deplist); $caid = sprintf("%03d",$caid); $file = "mips-".$caid.$campn.".analysis.php"; // END PHP. ?> <? echo "MIPS-$caid, Campaign $campn IOC/SV Analysis"; ?>

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Task Outcome Summary

Abstract

This task has a variety goals, depending on your level of ambition. The primary goal was to obtain a set of reference data to be used for assessing possible changes in the CSMM gain. The secondary objective was to measure the CSMM gain over a very large range of scan mirror angles. The goals of this task were not fully met for a couple of reasons. First, the 70um target star was too faint. We used an 0.25 Jy source, and we should have used something about 10-20 brighter. Second, optical distortions change the plate scale, so we need to use Code V to determine the plate scale at all regions of interest. We have no strong need to know the plate scale at the 24um pickoff mirror edges, so that analysis will not be done. In any event, measurements of the POM edges are much less accurate than stellar centroid measurements, so high precision measurements are not possible from the 24um data. Without 70um detections in SED, NF, and WF mode, we have nothing else to measure. If we had seen the same source in all three of those modes with just scan mirror moves between modes and no spacecraft moves, we could have measured the gain over almost the full scan mirror range. For the plate scale within SED, 70um NF, and WF modes, the FPS uses both spacecraft and scan mirror moves to determine the plate scale, which is a much cleaner approach. It is also noteworthy that there was a commanding error that resulted in slightly different scan mirror pointing than was desired.

Analysis

Since no star measurements were possible, the analysis involved two types of measurements. First, for maps over the 24um +Y and -Y pickoff mirror edges, the edge position was measured by stepping across the edge in xsloper_view and looking for the edge. Second, for WF and NF imaging, the positions of dark spots on the POM were measured, again using xsloper_view and determining the positions of the low flux spots. Neither method is all that accurate. The errors in the gain measurements are expected to be about 5%. For comparison, I looked up the scan mirror gain values predicted by Jerry Heim, as shown in the presentation he gave at an IOC meeting in 2002.

To calculate the scan mirror gain, the following steps were followed. Multiply the offset in pixels by the platescale in arcseconds per pixel (provided by Jane Morrison, based on Code V models). Divide by the stepoffset from the CESCANCON command (equal to 545 for all but the first dataset). The stepoffset is the number of relpos counts (or LSBs) between scan mirror positions. Finally, multiply by 32.635 to convert from arcseconds per LSB on the sky (typically about 0.07) to arcseconds of scan mirror tilt per LSB (typically 2.3).

Results

The measurements of gain produced the following results. The agreement with the predicted values is much better than I expected given my estimated error of about 0.1"/LSB. 

DataSet  ScanPos  ScanAbs  Gain("/LSB) Predicted  Method
   1        41      3220      2.34       2.41     POM
   2        36      3198      2.41       2.41     POM
   3         1      2007      2.18       2.20     Spots
   4        61       875      ---        2.56     (dark)
   5        39      1288      2.48       2.35     POM
   6        37      1435      2.28       2.29     POM
   7        38      2506      2.29       2.22     Spots
                              2.4                 70um POM

Conclusions

By direct measurement over a wide range of scan mirror angles, we have confirmed that the scan mirror gain varies roughly as predicted. A much better assessment can be made based on the various IOC focal plane surveys. The main goal of this test -- seeing the same star in 70um WF, NF, and SED modes with no spacecraft moves -- was not accomplished due to the choice of too faint of a calibrator star. We need to decide whether to repeat a subset of this test with a brighter 70um calibrator star. That test would provide a baseline dataset that could be used throughout the mission for determining whether there has been any shift in the scan mirror gain.

Output and Deliverable Products

None.

Actions Following Analysis

None.