Mission Planning for the Performance Verification Phase
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Contents |
[edit] Introduction
This document contains the detailed plan for the performance verification phase of TAUVEX. This phase begins 30 days after launch and will continue for 2 months.
[edit] Co-alignment
This is done in order to find out the co-alignment of the 3 telescopes of TAUVEX.
Procedure: All telescopes will be observing the same field simultaneously.
Location: Alessi 24
This field has negligible straylight.
R.A. - 17 24 01
Dec - -62 51 48
Orbits: 1
[edit] Coincidence Loss
In order to correct for the coincidence loss, we have to observe a field with number of stars of different brightnesses.
Location: Alessi 24
R.A. 17 24 01
Dec -62 51 48
orbits: 1
Telescope || Filter
T1 || SF1
T2 || SF1
T3 || SF2
shade
Telescope|| Filter
T1 || SF2
T2 || SF1
T3 || BBF
[edit] PSF measurement
PSF varies with count rate. Therefore field contains many stars with different count rates.
Location:
Orbits:
[edit] Distortion analysis
We have to create a set of displacement vectors. An ideal field would be the same field used for the PSF measurement.
Procedure:
Location:
Orbits:
[edit] Stray light measurements
[edit] Photometric calibration
From the list of 27 HST standard stars we will select those that are suitable for observation during the second month after the TAUVEX launch.
[edit] Schedule
[edit] Scheduling Philosophy
1. First 2 orbits---evaluation of the intrinsic background of detectors.
The background count distribution on the TAUVEX detectors may possibly be composed of two separate components. The first (typically referred to as the 'intrinsic' background) is an approximately uniform distribution of counts caused by the beta decay of 40K in the MCP glass as well as energetic particles in the spacecraft environment. This component may vary depending on the level of solar activity and the details of the spacecraft orbit. While the orbital averaged intrinsic count rates may vary over periods of weeks or months, there will be small changes during individual observations. The second component can be caused by scattered light, primarily the solar light reflected off the S/C components, mainly the solar panels. This component will vary substantially in strength during the orbit. Therefore, the first task would be to determine the level of the dark current and the variation of the dark current with the orbital stages. The second task is to map the solar straylight variations, which may be substantial if the closed filters have a leak. Therefore, the first two orbits will be performed with closed filters in the region with little UV sources to:
a). Determine the dark current;
b). Evaluate the leak the closed filter may have;
c). Map the solar SL that may influence the dark current even with closed filters.
If the leak and/or variation of the dark current is substantial --- it will give the first indication of the high strayligt parts of the orbit and in this case the procedure has to be written to deal with the faulty opaque filter.
Day 1. Nov. 1st '08
Filters: All closed
Region: FOV centered on the North Pole, declination: +90 degrees.
Time schedule:
HVPS on: 18.00 slt Continue till 04.00 slt.
04.00 - 06.00 --- Continuous monitoring of the counts level.
If counts level increase upto 15,000-20,000 per sec: it means that there is a strong leak in a closed filter. In this case - Move the MDP to the equator:
Declination: 0 degrees, till 06.00, after that move the MDP back to the NP.
If counts level remains small: keep on the NP full day.
Day 2. Nov. 2nd '08
Filters: All closed
Region: FOV centered on the North Pole, Declination: +90 degrees
Repeat the Day 1.
2. Next 3 orbits---mapping the straylight.
Keeping in the area with little UV sources, low transmission filters (SF1, NBF)---North Pole, we will evaluate the solar straylight for the whole orbit with possible turning the MDP or closing the filters according to the dark SL map obtained during the first 2 orbits. Since the telescopes will be open, we can perform the alignment test, and other calibrations.
Day 3. Nov. 3rd '08
Filters: T1: SF1, T2: SF1; T3 - NBF
Region: FOV centered on the North Pole initially. Declination: +90 degrees.
Time: 18.00 - open the filters.
Observe the NP: 18.00-01.00
Monitor the solar panels blocking the FOV 01.00-04.00
04.00 - 06.00 (scaterring is high) - go to other locations from declination range: -20 - +30 (to perform other calibrations - TBD).
06.00 - switch off the HPVS till 13.00 ---7 hours out - HAS to be checked!!!
13.00 - HVPS on, go to high declination range: +80 - +90 (to perform other calibrations---TBD) .
Continue till 18.00 slt.
Day 4. Nov. 4th '08
Filters: T1: SF1, T2: SF1; T3: NBF
Repeat the Day 3 procedure, to verify the effect of the solar panels blockage.
Day 5. Nov. 5th '08
Filters: T1: SF1, T2: SF1; T3: NBF
Repeat the Day 3-4 procedure, to verify the effect of the solar panels blockage.
[edit] Table
The schedule for the different calibration observations is given in the table. The R.A. range gives the observable R.A. values depending on the amount of straylight.
| Date | Purpose/Object | R.A. | Dec | R.A. range(hrs) | Telescope-Filter |
| 1 | data testing | closed | |||
| 2 | offset measurement | closed | |||
| 3 | Dark count | closed | |||
| 4 | First light | -90 00 00 | 9.7-19.9,21.7-5.0 | T1SF1,T2SF1,T3SF2 | |
| 8 | Calibration | 17 24 01 | -62 51 48 | 13-19.9,21.7-1.0 | T1SF1,T2SF1,T3SF2 |
| 8 | Calibration | 17 24 01 | -62 51 48 | 13-19.9,21.7-1.0 | T1SF2,T2SF1,T3BBF(shade) |
| 9 | NGC7793 | 23 57 49.7 | -32 35 30 | 23.1-1.0 | T1SF1,T2SF1,T3SF2 |
| 10 | NGC 5236 | 13 37 0.8 | -29 51 59 | 13.4-23.1 | T1SF1,T2SF1,T3SF2 |
| 10 | NGC 7293/HSTstd | 22 29 38.46 | -20 50 13.3 | -20-23.1 | T1SF1,T2SF1 |
| 28 | SDSS-South1 | 22 39 55.1 | -10 06 45 | T1SF1,T2SF1,T3SF2 |
| Date | Purpose/Object | R.A. | Dec | R.A. range(hrs) | Telescope-Filter |
| 17 | SDSS-South2 | 02 00 00 | -10 00 00 | T1SF1,T2SF1,T3SF2 | |
| 25 | GOODS | 03 32 30.37 | -27 48 16.8 | 2.7-4.0 | T1SF1,T2SF1,T3SF2 |
