Principal: Chad Engelbracht
Deputy: Dean Hines, Dave Frayer, Susan Stolovy
Data Monkey(s): Kate Su, Eiichi Egami
Priority: Necessary
Downlink Priority: Normal
Analysis Time: 2 weeks
Last Updated:
This tasks compares flux standards of similar brightness on differing backgrounds to check for background-dependent calibration changes.
Three standards will be observed in each of the 24, 70, and 160µm bands. The standards in each band will be of similar brightness but observed against as wide a range of backgrounds as possible. The observations will be made using the standard photometry AOR as in tasks 920, 922, and 924, using 3-second DCEs.
The targets were chosen to be of similar brightness (less than a factor of 2 between faintest and brightest) for a given band, to cover a wide range of backgrounds (this was typically a factor of 2 for our current list of potential calibrators), and to be detectable in a single DCE at a high ratio of signal to noise (the limit was set to 20 at the highest background).
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Candidate Stars |
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| ID | type | RA | DEC | Band | flux | bkgd. | visibility |
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(2000) | (2000) | (um) | (mJy) | MJy/sr | |
| HD181655 | G8V | 19:19:39.0 | 37:19:50 | 24 | 93 | 16.7 | 2003/08/24-2003/11/17 |
| HD58142 | A1V | 07:26:42.9 | 49:12:41 | 24 | 103 | 30.5 | 2003/09/28-2003/11/13 |
| HD173398 | K0III | 18:40:56.4 | 62:44:58 | 24 | 180 | 15.3 | 2003/08/24-2006/05/01 |
| HD217382 | K4III | 22:54:25.0 | 84:20:46 | 70 | 260 | 11.5 | 2003/08/24-2004/04/04 |
| HD189276 | K5Iab | 19:55:55.4 | 58:50:45 | 70 | 280 | 6.1 | 2003/08/24-2004/01/21 |
| HD163588 | K2III | 17:53:31.7 | 56:52:22 | 70 | 340 | 4.8 | 2003/08/24-2006/05/01 |
| HD056855 | K3Ib | 07:17:08.6 | -37:05:51 | 160 | 490 | 29.3 | 2003/10/06-2004/01/11 |
| HD048915 | A0V | 06:45:08.9 | -16:42:58 | 160 | 530 | 60.4 | 2003/09/25-2003/11/20 |
| HD045348 | F0II | 06:23:57.1 | -52:41:44 | 160 | 610 | 11.3 | 2003/08/24-2004/05/31 |
All observations for this task use the photometry AOT and 3s DCEs. 2 cycles are performed at 24µm, 3 at 70µm, and 2 at 160µm in superresolution mode, for a total of 6 cycles at 160µm. The number of images of each source is 30 at 24µm, 30 at 70µm, and 12 at 160µm. The AOT takes 1.2 hours, slightly more than the 1 hour allocated for this task.
Array Data Desired:
All Arrays
Data Reformatting Option:
Special Instructions:
This task as orginally envisioned does not belong where it has been placed in the timeline. It requires that the array biases have been optmized already (MIPS-245 and MIPS-246), a task that is not complete until campaign I, the next campaign after the campaign in which MIPS-921 is executed. It also requires the prelimary photometry AOT checkouts (MIPS-320, MIPS-322, MIPS-324) to be done, but the 160µm AOT checkout (MIPS-324) is being done in the same campaign and thus will not be done in time to execute this task. Thus, the goals of this task will have to be modified slightly. Only the 24µm results can be anticipated with the same confidence applied to most of the IOC tasks - the Ge:Ga analysis is subject to caveats, as discussed in the "analysis" section.
The data will be analyzed in a manner identical to the individual flux calibration tasks MIPS-920, MIPS-922, and MIPS-924. This will generate flux conversion factors for the 9 stars. The conversion factors will be compared to assess the effects of background levels on the measurements. As we are only measuring 3 stars per band, the report will not go into great detail on background effects. At this stage, a plot of flux conversion factors vs. background will probably be sufficient.
At the time this task will be executed, the Ge:Ga array biases have not yet been optimized and the 160µm photometry AOT has not yet had a preliminary checkout. Thus, the quality of the Ge:Ga data are subject to some uncertainty. This will be our first look at superresolution data on the 160µm array and thus I have allocated additional analysis time to allow us to respond to unforseen problems with this mode. The report will thus likely be released in stages: the 24µm portion can probably be done in a few days, with the 70µm portion following several days after. The 160µm report depends on the perfomance of the as-yet untested photometry mode. The measurements are being made in superresolution mode to move the source onto many different portions of the array and thus to provide some confidence that enough good measurements will exist to support the goals of the task.
The most likely problem area for this task is the 160µm measurements. The AOT has not been checked out by the time this task runs, so the quality of the 160µm data is subject to some uncertainty. The data will be taken in superresolution mode to place the source in many different positions on the array to hedge against problems with that array, but if there are problems with the data it will be necessary to repeat the parts of this task which failed.