MIPS IOC Summary March 6, 2001 Chad Engelbracht INTRODUCTION The MIPS IOC tasks can be broken into three main categories: Functionality, Characterization, and Calibration. We will describe these categories in turn and indicate which IOC tasks perform the functions listed. FUNCTIONALITY These tasks verify that the instrument responds to commands correctly, that the basic capabilities are available, and that the performance is as expected. - verify instrument aliveness These tasks perform the basic system checkout: Are the detectors alive (MIPS-010)? Can we power up and perform some simple commanding, including skeleton AOTs (MIPS-015)? Do the heaters, temperature sensors, and anneals work as expected (MIPS-30)? Do the 24um (MIPS-115) and Ge:Ga arrays (MIPS-247) respond to stimulators and do all the stimulators work? We also need to verify that the telemetry, for example that which tracks the operation of the scan mirror, is behaving as expected (MIPS-015). - verify basic throughput of optics and alignment Can we detect a star at 24um (MIPS-100), 70um (MIPS-101), and 160um (MIPS-102)? - measure stability of read noise and dark current To assess stability, task MIPS-225 monitors performance during instrument start-up and also compares this performance from start-up to start-up by taking a standard set of data. This task should be renamed from "Instrument Stability" to something more specific to what it actually does. Later on in IOC, we will measure the stability of read noise and dark current throughout and between instrument campaigns using MIPS-260, MIPS-261, and MIPS-262. - focus confirmation Task MIPS-121 performs a focus check at 24um using a few stars. If necessary, MIPS-122 will be used to follow up with a focus check at 70um fine scale. MIPS-123 outlines a focus check at 160um which won't tell us anything new and so can be deleted. - verify operation of AOTs The initial instrument checkout discussed in MIPS-015 performs a simple skeleton AOT validation of all 4 modes to check that the commanding and dataflow are functioning as expected. Once the telescope has cooled down, we can check out the skeleton SED (MIPS-300) and Total Power (MIPS-330) AOTs in more detail using astronomical sources. We can also perform the full AOT validation for Photometry (MIPS-320) and Scan Map (MIPS-325). Task MIPS-355 will be used to confirm that the cluster option works correctly for all AOTs. Part of the analysis of all the AOT validation data will be to determine if any tweaks (e.g., in pointing, scan mirror parameters, or spacecraft slew rates) are required, but these analyses are not discussed explicitly in the current task definitions (but they should be). The AOT verification should also include a test that pushes the data handling system by taking data in a mode that generates a large amount of data in a short amount of time. This may mean taking some data in RAW mode for each AOT as a test, something which is not done in the current task definitions. - verify command expansion and data handling As discussed, MIPS-015 includes a checkout of the state transition and AOT commanding. MIPS-110 will be used to confirm that 24um slope-fitting and Ge:Ga coadding are functioning as expected. CHARACTERIZATION These tasks include characterization of low-level instrument behaviors that will dictate how we optimize the instrument operation and data reduction. As part of the process, these activities also characterize the on-orbit environment and sky properties. - optimize operating parameters These tasks optimize the DC offset for the A/D converters (MIPS-125), determine the optimum bias settings (MIPS-245), determine the cosmic-ray limits on integration times (MIPS-250), and determine the optimum operating temperature for the 24um array (MIPS-345). A task we've left off this list is optimization of the stimflash interval. It's possible that the data collected for other purposes will be sufficient to evaluate this, but those data will likely be dominated by only a few stimflash intervals (~20s, 1m, and 2m). A dedicated test is likely needed. - latent images and saturation These tasks characterize latent image and saturated source behavior at 24um (MIPS-155) and on the Ge:Ga arrays (MIPS-210), using astronomical sources. We will also perform a check to ensure that slewing over an extremely bright source will not affect subsequent data (MIPS-220). - electronic nonlinearity MIPS-180: the data generated by this test should be ideal to also confirm the dynamic range of the Ge:Ga arrays. - stimulator nonlinearity NO tasks currently defined. - detector/system nonlinearity Task MIPS-400 performs the initial screening of standard star candidates and so measures many different stars with a wide range of fluxes. Those data can be used to check the detector nonlinearity. Task MIPS-150 currently duplicates much of MIPS-120, the initial flux calibration at 24um, but it also includes comparisons of sources observed in different modes. MIPS-150 should be expanded to include a comparison of several calibration sources in all 4 MIPS observing modes, to measure a sort of "system" linearity, e.g., do we get the same answer for a star measured in photometry, scan map, SED, and total power? - anneal frequency and effectiveness Task MIPS-160 will characterize the performance changes on the Ge:Ga arrays as cosmic-ray induced damage accumulates and allow us to optimize the anneal frequency. Task MIPS-165 will assess the effectiveness of the bias boost and photon flood anneals as compared with the thermal anneal. - ghosts / scattered light measurement We will measure the scattered light background several times as the telescope cools down (MIPS-050, MIPS-055, MIPS-060, MIPS-065, and MIPS-070). A similar measurement will be made after everything has cooled off, while pointing at the ecliptic pole, to measure the ultimate scattered light level (MIPS-340). We will also perform a brief search for off-axis glints (MIPS-310). We will characterize ghosts using standard star and saturated source data taken throughout IOC. - point spread function / SED slit profile Of course, we want to know the detailed SED slit profile (MIPS-140) and measure an accurate PSF at all wavelengths (MIPS-335). The PSF task may need a second look - it lists asteroids as the only target and it's not clear why we wouldn't want to use stars to do this. Also, the analysis should include a study of charge bleeding and scattered light effects, which isn't explicitly discussed in the current task. - AOT optimization These tasks test the limits of the AOTS by observing various astronomical targets such as circumstellar disks (MIPS-135, MIPS-275), faint backgrounds (MIPS-270), outflows (MIPS-280), extended nebulosity (MIPS-285), star formation regions (MIPS-290), and large extended sources (MIPS-295). Task MIPS-148 characterizes the illumination gradient (if any) throughout the SED region. It is in these tests that we will confirm that any tweaks suggested by the AOT commissioning tasks (e.g., in the pointing or scan mirror parameters) perform as expected. - spectral leaks Task MIPS-240 compares observations of a blue source (a star) and a red source (an asteroid) to check for spatial frequencies indicative of a short- wavelength leak. This test should be a short version of the detailed PSF measurement (MIPS-335). - performance (sensitivity, confusion, background) Task MIPS-255 checks the flux calibration stability and so largely duplicates task MIPS-350. This task can probably be deleted. Task MIPS-265 measures the confusion limit at 160um and possibly at 70um, while task MIPS-315 analyzes the behavior of various MIPS features (e.g., latent images, stability) as a function of background level. - determine array geometry and measure distortion, platescale These tasks (MIPS-130, MIPS-131, MIPS-132, MIPS-133, and MIPS-235) essentially describe the focal plane survey. Also included is a coarse survey (MIPS-139) to find the SED slit. - droop While it will be difficult to accurately measure the droop coefficient of the 24um array in orbit, we would at least like to verify the measurement we made on the ground. One way to do this is to use the data taken for the standard star screening test, MIPS-400. If we aren't performing the droop correction accurately, stars of similar brightness but on different backgrounds will produce very different results. Another, perhaps cleaner, way to check this would be to observe the same star under different background conditions, by observing it both with and without the 24um stimulator on. The star would have to be carefully chosen so as not to saturate with the stim on, but the initial 24um stimulator calibration test (MIPS-120) could easily be written in such a way as to accomplish this task, too. - scan and photometry illumination correction comparison We think we can use scan mode to generate routine illumination corrections for both scan and photometry mode, but we don't yet have a task which demonstrates this to be true. We should add one. - point vs. extended source calibration Although MIPS instrument requirements don't include extended source calibration, we will make a check to see how well we can calibrate a modestly extended source. This test is included in the relative throughput test (MIPS-150). - optimize spacecraft slew rate We don't currently have a task that optimizes the spacecraft slew rate to match the CSMM scan rate, so we should add one. CALIBRATION These tasks allow us to characterize (and remove) high-level instrumental signatures from the data and provide the pipeline with the data needed to perform an accurate flux calibration on all parts of the array. These data are needed not only for routine operations but for calibration of other IOC tasks, so it is very important that task principals indicate what calibration data they are expecting to be available for the analysis of each activity's data. - spectral response This task has no MIPS-specific template. To confirm that our spectral response is as expected, we should make sure that both red and blue sources observed for cross calibration produce the same answer with MIPS and IRS. - flat field and illumination corrections The task MIPS-305 performs the standard flat field or illumination correction measurement that will also be used in regular operations. This task also discusses a check of the flat fielding using observations of a star, which would not be included as part of the routine flat measurement, so we should explore moving that flat-field check into a separate task or perhaps using other data (such as the focal plane survey) for that purpose. - dark current The tasks MIPS-260, MIPS-261, and MIPS-262 outline 3 measurements of read noise and dark current to check for stability. The dark current measurement part should simply use the dark IER that will be used during routine operations, but these task descriptions don't say that explicitly. - responsivity Task MIPS-120 performs an early check of the 24um array flux calibration. Later on, when the telescope is cold enough to start using the Ge:Ga arrays, we will use the standard flux calibration activity, MIPS-350, to calibrate all three arrays as they would be calibrated during routine operations. Task MIPS-400 performs the initial screening of flux standards for contamination by disk emission, background sources, or other problems, and so should be run before MIPS-350. - wavelength calibration Task MIPS-145 measures a couple of PNe and a couple of HII regions to get lines bright enough to centroid on and confirm our wavelength calibration. - routine calibration Later in IOC and as we make the transition into routine operations, we will want to perform certain tasks every time we turn the instrument on. Such tasks include things like flux calibration, dark current measurements, and flat field measurements. We've tried to keep track of this in a crude way by listing some of those tasks several times, but this is an area that needs some attention. For example, some of the tests described here implicitly assume that we'll have calibration data available, but our current IOC structure doesn't guarantee that such data will be available for the particular campaign in which your IOC task gets executed. A suggestion for starting to deal with this issue would be to carefully document in each task writeup what calibration data are needed. As a backup, we should also default (whenever possible) to taking a standard set of calibration data every time we turn on the instrument so that we can support further tests that we haven't thought of yet with the data that we've already taken for other reasons. TASK SUMMARY as of 3/06/01 MIPS-010 MIPS Detector Aliveness Check MIPS-015 Combined Electronics State Validation and Functional Tests MIPS-030 Heaters, Temperature Sensors MIPS-050 MIPS Scattered Background Monitor -- Part 1 MIPS-055 MIPS Scattered Background Monitor -- Part 2 MIPS-060 MIPS Scattered Background Monitor -- Part 3 MIPS-065 MIPS Scattered Background Monitor -- Part 4 MIPS-070 MIPS Scattered Background Monitor -- Part 5 MIPS-100 MIPS first light at 24um MIPS-101 MIPS first light at 70um MIPS-102 MIPS first light at 160um MIPS-110 Confirmation of MIPS On-board Data Processing Algorithms MIPS-115 MIPS 24um Detector Response to Stimulators MIPS-120 Calibration of MIPS Stimulators Against Celestial Sources at 24um MIPS-121 MIPS Focus Confirmation -- Part One at 24 microns MIPS-122 MIPS Focus Confirmation -- Part Two at 70 microns MIPS-125 MIPS Transfer Function Test MIPS-130 24 um Array Geometry and Scan Mirror Vectors (Coarse) MIPS-131 24 um Array Geometry and Scan Mirror Vectors (Fine) MIPS-132 70 um Wide Field Array Geometry and Scan Mirror Vectors (Coarse) MIPS-133 10 MIPS 70 um Wide Field Array Geometry and Scan Mirror Vectors (Fine) MIPS-135 10 MIPS MIPS Spectral Energy Distribution of a Circumstellar Region MIPS-137 70 um Narrow Field Array Geometry and Scan Mirror Vectors (Coarse) MIPS-138 70 um Narrow Field Array Geometry and Scan Mirror Vectors (Fine) MIPS-139 MIPS SED mode slit location and orientation MIPS-140 MIPS SED mode slit profile MIPS-145 MIPS SED mode wavelength calibration. MIPS-148 SED Illumination Determination MIPS-150 Relative Throughputs of Different Observing Modes MIPS-155 Characterize MIPS Latent Images and Saturated Source Behavior at 24um MIPS-160 MIPS 70 and 160 um Thermal Anneal Behavior MIPS-165 MIPS Non-Thermal Anneal Assessment MIPS-180 MIPS Electronic Nonlinearities Verification MIPS-210 MIPS 70um and 160um Behavior of Saturation and Latents MIPS-220 MIPS Slew State Validation MIPS-225 Instrument Start-up Transient Behavior, 24um MIPS-226 Instrument Start-up Transient Behavior, 24um and Ge Arrays MIPS-234 MIPS 160um Array Location and Orientation MIPS-235 160mu array geometry MIPS-240 MIPS spectral leak checks MIPS-245 Optimum Bias Setting for MIPS Detectors MIPS-247 MIPS 70 and 160 um Detector Response to Stimulators MIPS-250 Cosmic-ray limits on integration times MIPS-260 MIPS Read Noise and Dark Current Stability 1 MIPS-261 MIPS Read Noise and Dark Current Stability 2 MIPS-262 MIPS Read Noise and Dark Current Stability 3 MIPS-265 MIPS Scan to Determine Confusion Limits MIPS-270 MIPS Total Power Measurement at the Ecliptic Pole. MIPS-275 MIPS Photometry of a Circumstellar Region MIPS-280 MIPS Super Resolution of the SVS-13 Source in the HH 7-11 Region MIPS-285 MIPS Scan Map of a Large Planetary Nebula or Supernova Remnant MIPS-290 MIPS Scan Map of the HH 7-11 Region MIPS-295 MIPS Scan Map of M31 (or M33) MIPS-300 MIPS Spectral Energy Distribution Skeleton AOT Validation MIPS-305 Production of Pipeline-quality Illumination Corrections (Ge) and Flatfields (Si) for MIPS MIPS-310 MIPS Off-axis Glints MIPS-315 MIPS Behavior as a Function of Sky Background MIPS-320 MIPS Photometry/Super Resolution AOT Validation MIPS-325 MIPS Scan AOT Validation MIPS-330 MIPS Total Power Mode Skeleton AOT Validation MIPS-335 MIPS Point Spread Functions MIPS-340 Determination of Ultimate MIPS Scattered Light Levels MIPS-345 Optimum Operating Temperature for the MIPS 24um Array MIPS-350 MIPS Flux Calibration 1 MIPS-351 MIPS Flux Calibration 2 MIPS-352 MIPS Flux Calibration 3 MIPS-355 MIPS AOT Cluster Option Validation MIPS-400 MIPS Flux Standard Screening and Linearity Check