Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2141c Report Date: 09-May-96:16:53 Version: ********** Check-in Date: ********** 1.Proposal Title: SPACECRAFT GLOW MEASUREMENT TEST ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SV/OLT Sub Category ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Pierre Bely ST SCI USA (301)338-4780 ------------------------------------------------------------------------------------ 7. Abstract Test Objective: Measure the broadband intensity and spectral distribution of HST induced glow (i.e., "shuttle glow") resulting from its passage through the ambient upper atmosphere. Determine the glow intensity dependence on the HST spatial orientation relative to the HST orbital parameters. This test will be repeated after 6 months to study outgassing effects. Rev 1/89,4/89. Revised 3/21/90 by PStanley to delete REPEAT requirement on line 11. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 6.00 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOC WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2141c PI: Pierre Bely Proposal Title: SPACECRAFT GLOW MEASUREMENT TEST ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Olivia Lupie ST SCI USA P.I. Pierre Bely ST SCI USA X Francesco Paresce ST SCI USA X John Clarke MSFC USA Bruce Toth STSCI USA Robert O'Dell RICE UNIVERSITY USA ------------------------------------------------------------------------------------ 2. Scientific Justification. Test Description: The "spacecraft glow" effect in the HST environment could introduce a spurious background in the observations of all HST science instruments particularly for long exposures of very faint objects. At present, there is no mission constraint to limit observations when this effect may be present, that is, at times when the in-plane HST velocity vector points in the vicinity of the targets. This test is designed to measure the intensity and the wavelength characteristics of any S/C glow that may be present under this worst case condition. Because of the faintness of the phenomenon (predicted to be 25th magnitude per arc second square in the red), this OLT must be performed under minimum conditions of background and stray light illumination. All target and environmental constraints are described in detail in GF #5. ------------------------------------------------------------------------------------ 3. Description of proposed observations. To allow differentiation from the background and characterization of the glow with the attack angle (angle between the HST velocity vector and line of sight), 3 WFC 8-minute exposures will be obtained contiguously while in shadow. The first of the exposures must start as soon after target rise as possible. Note that the Dark requirement may be lifted on the 3rd observation if the last 1-2 minutes of that observation falls outside of shadow. The wavelength dependence of the glow will be measured by repeating the observations with different filters over 2 additional orbits and then observing with the FOC during a fourth orbit. Because of the target faintness, a WF/PC bias and dark frame are required before and after each set of observations during each orbit. Orbit 4 FOC exposures will provide attack angle dependence of Lyman-alpha glow in UV. The LOS will be parallel to the HST velocity vector 4 minutes after the start of first observation of the second orbit. This requirement (described further in GF.5) allows the attack angle to be about equal to zero at the midpoint of the first observation of the second orbit, and near but equally displaced from zero during the first exposure of the other orbits. The pointing is fixed and the same for all measurements in this test. GYRO Tracking is acceptable and requested. **Attack Angle, Orbit Geometry, and Test Design** The velocity vector sweeps an angle of about 30.5 deg in 8 minutes. The angle between the LOS and the velocity vector, at the mid-point of an 8 minute exposure is 0, 50, and 100 degrees for the 1st, 2nd, and 3rd exposures respectively, in an orbit. The horizon drop-off angle for the HST orbit is about 22.5 degrees. This means that for an LOS coincident with the velocity vector at the midpoint of an observation will intercept the earth's limb at the start of the observation if the exposure duration is longer than 11.5 minutes. For an 8 minute observation, the target LOS will be about 7 degrees above the earth's limb at the start of the observation. Note that the variation in the attack angle due to the orbital precession over four orbits is less than 2 degrees. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Submitted as an Observatory Level Test ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The scheduling constraints on this test are listed in the following sections. The target will be described as a moving target but with a fixed pointing. *****Test Schedule Constraints: 1) Minimize scattered light from earth and moon: - Phase of moon: between new (- 2 days) or first quarter (+ 2 days). - Target observations taken during DARK TIME (spec. req). 2) Minimize zodiacal light - orbital velocity vector points furthest from the ecliptic (within +/- 10 degrees of plane). Limit observing times to those months of the year when this condition occurs (optimum months are Nov through January, May through July). 3) Minimize galactic background light by selecting those times when the velocity vector is >= 20 degrees from the galactic plane. 4) No data through the SAA 5) POINTING: First exposure in each non-int sequence to start as soon after target rise as possible within shadow. The target will be the direction of the velocity vector 4 (+/- 1) minutes after the START of this first observation of the Second orbit. This will be the pointing for all 4 orbits. 6) TRACKING: GYRO TRACK IS ACCEPTABLE AND REQUESTED. TARGET SPECIFICATION: Solar_System Level 1: FILE=VEL_EPHEM.DAT. SPSS to receive from proposers a file containing the target ephemeris containing 365 entries, one position per day for a year. This file will be generated from the predicted state vector file. A series of WINDOW intervals will accompany the data set. The WINDOWS will reflect the requirements of LOS with respect to ecliptic and galactic plane. The requirement on SPSS therefore, will be to sschedule the first observations per orbit as soon into earth shadow as possible and to take into account the lunar phase requirements. File Generation: the file data will be constructed from the epehemeris the HST velocity vector as a function of time and the time of earth shadow entry as a function of day in the year. The data set and window determination may be extracted from a state vector file and processed through specialized software we have constructed. CAUTIONS: Predicted HST orbit is required for a year and multiple updates to the ephemerides and the WINDOWS are required. ALTERNATIVE TARGET SPECIFICATION: Solar_System Level 1: STD = Orbit Pole Specification in this way relieves the external interface with SPSS and the manipulation of complex HST orbit data with numerous updates. Subsequent Level 2 and Level targets will be necessary to link the orbit pole with the orbit plane abd with the sun angle constraint. Similar Window requirements will be used to satisfy the constraints listed in section 5-2. This method is TBD pending potential scheduling system enhancements to: 1) accommodate the use of the 'Orbit -pole' as a standard target, 2) to devise a method to use level 2-3 'TYPE=XXXX' targets to describe an offset relative to the pole which puts the LOS into the orbital plane (90 deg) and then uses the direction to the sun to pin down the LOS at entry into umbral shadow. (ie, specify angle from sun vector - currently not achievable through the TYPE=PA_SUN specification in the current proposal instructions). --- TEST PREREQUISITES: o Level 1 optical image quality not required. (lambda/8 is sufficient) o Mini-OFAD verification is desireable but not necessary o WF/PC UV Flood and pre-flash capabilities operational (SV/1431) o WF/PC cooled to nominal operating temperatures (SV/1431) o WF/PC preliminary focus setting established (OV/1482) o FOC preliminary focus setting established (SV/1507) --CAUTIONS:-- When the number of potential targets locations are sufficiently minimized or selected, we must make a brightness alert check of the candidate fields for protection of FOVs. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Dark times are required for this OLT since the expected magnitude level of the S/C glow effect is extremely faint. Considerations of orbital geometry relative to the positions of the sun, moon, ecliptic plane and galactic plane and even the selection of an intrinsically dark portion of the sky as a target will all be required to insure meaningful measurements of the S/C glow. Page 4 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. Real Time Data Analysis Requirements: Not anticipated at this time. Offline Data Analysis Requirements: For WF/PC Exposures: o Process each of the 12 frames for bias subtraction and normalization for relative sensitivity variation (flat fielding). o Select the image area which is common to the 9 frames o Determine a single mean flux for each of the WFC and FOC images. Because the image will be contaminated by field stars and extended sources, the mean (or modal) flux level for the image is most easily determined from the spatial intensity distribution function. For each image, construct a histogram of the number of pixels above a given count as a function of the count rate. Determine the mode of the major component of the distribution which is the background. The corresponding count rate defines the mean flux of the background portion of the image. o Add all remaining pixels in each individual frames together o Compare aggregated intensities of the last frame of each orbit (reference frames) relative to each other and against zodiacal light to calibrate (or verify) OTA and WF/PC throughput efficiency as a function of wavelength. o Compare the results of the repetition of the test after 6 months to those of the original test to obtain possible time dependence effects. ------------------------------------------------------------------------------------ 11. Address Information Name: PIERRE BELY Category: PI Institution: ST SCI Address: 3700 SAN MARTIN DRIVE City: BALTIMORE State: MD Zip Code: 21218 Country: USA Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ Name: OLIVIA LUPIE Category: CON Institution: ST SCI Address: 3700 SAN MARTIN DRIVE City: BALTIMORE State: MD Zip Code: 21218 Country: USA Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2141c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 GLOW-TAR RA = 135.3087D +/-0.001D, J2000 1 SURF(V)=25 +/- 0.5 DEC = 27.7292D +/-0.001D Comments: CYCLE 0 OBSERVATION ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2141c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DEF BIAS WFC IMAGE ALL F850LP SUM=2X2 1 0 S 1 CYCLE 0 / 1-78 CALIB1 PRE-FLASH=YES ------------------------------------------------------------------------------------------------------------------------------------ 2 ^ ^ DARK ^ ^ ^ ^ ^ 1 8 M ^ ^ ------------------------------------------------------------------------------------------------------------------------------------ 7 DEF DARK FOC/96 IMAGE 512X102 F120M 1 8 M 1 1 CALIB2 4 ------------------------------------------------------------------------------------------------------------------------------------ 11 USE SEQ 11-78 WITHIN CALIB1 7.0 H SEQ 11-18 WITHIN 98 M CALIB FOR 12 SEQ 11-18 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ 12 GLOW-TAR WFC IMAGE ALL F850LP SUM=2X2 3 8 M 1 NON-INT PRE-FLASH=YES GUIDE TOL 6.0" Comments: CRITICAL SCHEDULING REQUIREMENTS; SEE GF QUESTION 5 ; FIRST EXPOSURE SHOULD BE SCHEDULED IMMEDIATELY AFTER SPACECRAFT ENTERS EARTH SHADOW. PCS MODE GYRO. ------------------------------------------------------------------------------------------------------------------------------------ 18 USE CALIB FOR 12 CALIB1 ------------------------------------------------------------------------------------------------------------------------------------ 31 USE SEQ 31-38 WITHIN CALIB1 98M CALIB FOR 32 SEQ 31-38 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ 32 GLOW-TAR WFC IMAGE ALL F702W SUM=2X2 3 8 M 1 NON-INT PRE-FLASH=YES GUIDE TOL 6.0" Comments: CRITICAL SCHEDULING REQUIREMENTS; SEE GF QUESTION 5 ; FIRST EXPOSURE SHOULD BE SCHEDULED IMMEDIATELY AFTER SPACECRAFT ENTERS EARTH SHADOW. PCS MODE GYRO. ------------------------------------------------------------------------------------------------------------------------------------ 38 USE CALIB FOR 32 CALIB1 ------------------------------------------------------------------------------------------------------------------------------------ 51 USE SEQ 51-58 WITHIN CALIB1 98M CALIB FOR 52 SEQ 51-58 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2141c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 52 GLOW-TAR WFC IMAGE ALL F555W SUM=2X2 3 8 M 1 NON-INT PRE-FLASH=YES GUIDE TOL 6.0" Comments: CRITICAL SCHEDULING REQUIREMENTS; SEE GF QUESTION 5 ; FIRST EXPOSURE SHOULD BE SCHEDULED IMMEDIATELY AFTER SPACECRAFT ENTERS EARTH SHADOW. PCS MODE GYRO. ------------------------------------------------------------------------------------------------------------------------------------ 58 USE CALIB FOR 52 CALIB1 ------------------------------------------------------------------------------------------------------------------------------------ 71 USE SEQ 71-78 WITHIN CALIB2 98 M CALIB FOR 73 SEQ 71-78 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ 73 GLOW-TAR FOC/96 IMAGE 512X102 F120M 10 50S 1 NON-INT 4 Comments: CRITICAL SCHEDULING REQUIREMENTS; SEE GF QUESTION 5 ; FIRST EXPOSURE SHOULD BE SCHEDULED IMMEDIATELY AFTER SPACECRAFT ENTERS EARTH SHADOW. PCS MODE GYRO. ------------------------------------------------------------------------------------------------------------------------------------ 78 USE CALIB FOR 73 CALIB2 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2141c [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC ^ FOC/96 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ^ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SUM=2X2 PRE-FLASH=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for SV/OLT ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 6.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 0 / 1-78; SEQ 11-78 WITHIN 7.0 H; SEQ 11-18 WITHIN 98 M; CALIB FOR 12; SEQ 11-18 NO GAP; NON-INT; GUIDE TOL 6.0" CALIB FOR 12; SEQ 31-38 WITHIN 98M; CALIB FOR 32; SEQ 31-38 NO GAP; CALIB FOR 32; SEQ 51-58 WITHIN 98M; CALIB FOR 52; SEQ 51-58 NO GAP; CALIB FOR 52; SEQ 71-78 WITHIN 98 M; CALIB FOR 73; SEQ 71-78 NO GAP; CALIB FOR 73; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F850LP ^ F120M F702W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GLOW-TAR ------------------------------------------------------------------------------------------------------------------------------------