8650( 4) - 05/08/00 09:10 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8650 Version: 4 Check-in Date: 08-May-2000 09:09:17 1.Proposal Title: The Interplanetary Medium Hydrogen Velocity Distribution ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: John Clarke University of Michigan CoI: Dr. Rosine Lallement Service d'Aeronomie du CNRS N CoI: Dr. Jean-Loup Bertaux Service d'Aeronomie du CNRS N CoI: Dr. Hans Fahr Universitat Bonn N CoI: Dr. Eric Quemerais Service d'Aeronomie du CNRS N CoI: Dr. Daniel Rucinski Space Research Center, Polish Academy of N Science CoI: Dr. Maciej Bzowski Space Research Center, Polish Academy of N Science CoI: Dr. Erkki Kyrola Finnish Meteorological Institute N CoI: Dr. Tuula Summanen Finnish Meteorological Institute N ------------------------------------------------------------------------------------ 5. Abstract Neutral atoms from the interstellar medium (ISM) flow into the solar system producing a diffuse emission at 1216 Angstrom by resonant scattering of solar H Ly- alpha emission. This wind contains the velocity distribution of the local ISM, plus modifications by solar gravity, radiation pressure, and ionization near the Sun, and the Ly-alpha emission line profile reveals these velocity signatures. Compared with the He flow at 26kms, consistent with the local ISM cloud, the H velocity of 18- 21kms suggests an additional alteration of the H atom velocity distribution by charge exchange at the heliospheric interface. In cycles 1 and 4 we obtained initial GHRS echelle A Ly-alpha line profiles in 3 look directions. For cycle 9 we propose three focussed observations, taking higher sensitivity STIS echelle spectra to address the following key questions about the interplanetary H: 1) we will accurately measure the ratio of solar gravity to radiation pressure on the flow, 2) we will obtain upwind spectra close in time to FUSE spectra of the optically thin Ly -beta emission to directly measure the optical depth, and 3) we will obtain high S/N line profiles upwind to determine the extent of slowing of the inflow velocity distribution indicated in earlier HST and SOHO observations. The end goals of this program are to characterize the properties of the local ISM and its modification at the heliospheric interface. ------------------------------------------------------------------------------------ 8650( 4) - 05/08/00 09:10 - [ 2] Observations Description ------------------------ From a cycle 7 program for observations of Jupiter, we have initial STIS E140H spectra with the 6 x 0.2 arc sec aperture including some region on the sky background, from which we can estimate the resolution and sensitivity of this observing mode. The efficiency of STIS is similar to that of the GHRS, so that the count rate scales nearly as the aperture area compared with the 1.74" GHRS LSA. A significant opportunity is presented since the STIS sky apertures will be supported in cycle 9 for echelle spectra. For these observations of monochromatic sky emission (in the Earth's shadow the oxygen airglow is too faint to detect), there is no complication from order overlap in the echelle spectra. For observations of diffuse emission, the 52 x 0.5 sky aperture will give a factor of 4.1 times increase in count rate compared with GHRS, with the aperture length of 25" limited by the MAMA detector. The corresponding FWHM resolution for diffuse emission is 0.057 Angstrom, as we have measured in our cycle 7 Jupiter obserivng program, giving the STIS spectra 30 percent higher spectral resolution than the existing GHRS LSA spectra. The integration time of 1 orbit per view direction is the same as what we have had with GHRS. For the upwind and crosswind directions, we will split the orbit between the two apertures, to obtain both high sensitivity for the wings of the IPH line and high spectral resolution to resolve the line core. The STIS observations require pointing only within roughly 10degrees of each direction on the sky, with no bright stars in the aperture, and can be made under gyro control or with fine guidance sensors. In practice, we select a nearby dark cloud for the STIS target to limit the possibility of any stellar emission falling in the aperture. These spectra would be taken in June 1999 and spring 2000 to optimize the Earth orbit direction for each line of sight. We will perform observations in the following lines of sight: - to determine value of Mu, observe crosswind in both directions with and against Earth orbit, to measure Mu and also determine inflow direction - schedule in June 2000 or June 2001 - observe upwind close in time with STIS and FUSE (looking at the IPH Ly-beta line) to determine optical depth of H column, and thereby determine H density and the corresponding ionization fraction of the local ISM - this will also provide absolute intensity of the upwind emission, and provide a measurement of the inflow speed and velocity distribution near solar maximum, compared with varying inflow speeds measured in the past from GHRS and SWAN - schedule in March-April 2001 Real Time Justification ----------------------- These spectra must be scheduled during HST dark time to minimize the geocoronal Ly-alpha brightness. The slowly varying geocoronal Ly Alpha does not require a sharp cut-off of the integrations at HST shadow passage. Note that the proposed lines of sight are roughly perpendicular or opposite each other, so we cannot observe more than one line of sight per orbit due to the limited HST slewing rate. The detector flat field and echelle wavelength calibrations will be available, and in this case there will be no other emissions except Ly-alpha falling on the detector, so there will be no order overlap. We can use wavelength lamp spectra with the same aperture/grating to calibrate our spectra. We have been awarded a FUSE cycle 1 GO program for observations of the sky Ly-beta emission (J. Clarke PI), which will be obtained with some time in spring or early summer 2000, and additional time in 2001. We will need to schedule some HST time within a few days of these observations, in the interest of seeing the same solar flux, but the slow flow speed of the IPH does not dictate any other requirement. If the observations are spaced apart by a longer period, we can still extrapolate from proxy data of solar activity, such as the He 10830 emission. We willalso preform coordinated observations between HST and the SWAN experiment on SOHO (Bertaux et al. 1997). It is not possible to observe the same line of sight with STIS and SWAN at the same time, since the STIS method requires a minimum velocity difference of 15-20 km/sec between the geocorona and the IPH to separate the lines spectrally, while the SWAN absorption cell has higher spectral resolution but a limited wavelength range requiring less than 30 km/sec velocity difference for inclusion of the IPH emission line. Fortunately, the time scale for the flow through the inner solar system is several months, allowing us to observe the same line of sight at times which differ by a few months without large changes in the flow pattern. We will request observations some multiple of 28 days apart, so that the same side of the Sun is pointed along the observing path for consistency. We have selected the crosswind line of sight, which will provide a velocity difference of 30 km/sec for STIS spectra in early June 2000 and also permit SWAN spectral scanning by spacecraft rotation in early 2000. The dominant selection factor of this line of sight has been the ease of observation with the two instruments, to permit us to obtain high quality spectral line profiles from each. Scheduling of the SWAN observations will be accomplished by the proposing team (co-investigator J.-L. Bertaux is PI for SWAN). Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8650( 4) - 05/08/00 09:10 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SKY-105936- ISM RA=10H 59M 36S +/- 1', DEC=00D J2000 SURF-LINE(1216)=2.+/-1.e-12 001920 19' 20" +/- 1', REGION W-LINE(1216)=0.15+/-0.1 V = 18 Coordinate Source: OTHER_SOURCE Comments: STIS SPECTRA OF INTERPLANETARy HYDROGEN, I.E. OBSERVE SKY WITH NO STARS MV < 18 IN APERTURE, LOOKING ACROSS THE FLOW. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0 0.0 0.0 2 SKY-225730- ISM RA=22H 57M 30S +/- 1', DEC=00D J2000 SURF-LINE(1216)=2.+/-1.e-12 000600 6' 0" +/- 1', REGION W-LINE(1216)=0.15+/-0.1 V = 18 Coordinate Source: OTHER_SOURCE Comments: STIS SPECTRA OF INTERPLANETARy HYDROGEN, I.E. OBSERVE SKY WITH NO STARS MV < 18 IN APERTURE, LOOKING ACROSS THE FLOW. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0 0.0 0.0 3 SKY-165050- ISM RA=16H 50M 50S +/- 1', DEC=-15D J2000 SURF-LINE(1216)=2.+/-1.e-12 152548 25' 48" +/- 1', REGION W-LINE(1216)=0.15+/-0.1 V = 18 Coordinate Source: OTHER_SOURCE Comments: STIS SPECTRA OF INTERPLANETARy HYDROGEN, I.E. OBSERVE SKY WITH NO STARS MV < 18 IN APERTURE, LOOKING UPWIND. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0 0.0 0.0 8650( 4) - 05/08/00 09:10 - [ 4] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 20-Jun-2000 AND 10-Jul-2000 On Hold Comments: Additional Comments: Please schedule as close as possible to 01-JUL-2000 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SKY-105936- STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=4000. 1 2450 S 001920 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8650( 4) - 05/08/00 09:10 - [ 5] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 20-Jun-2000 AND 10-Jul-2000 On Hold Comments: Additional Comments: Please schedule as close as possible to 01-JUL-2000 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 2 SKY-225730- STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=4000. 1 2450 S 000600 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8650( 4) - 05/08/00 09:10 - [ 6] Visit: 03 Visit Priority: Visit Requirements: BETWEEN 20-Mar-2001 AND 10-Apr-2001 On Hold Comments: Additional Comments: Please schedule as close as possible to 01-APR-2001 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 3 SKY-165050- STIS/F TIME-TA 52X0.5 E140H 1234 BUFFER-TIME=4000. 1 2450 S GS ACQ SCENARIO SINGLE 152548 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8650( 4) - 05/08/00 09:10 - [ 7] Summary Form for Proposal 8650 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=4000. ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 20-Jun-2000 AND 10-Jul-2000 BETWEEN 20-Mar-2001 AND 10-Apr-2001 GS ACQ SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140H ------------------------------------------------------------------------------------------------------------------------------------ Target Names SKY-105936-001920 SKY-225730-000600 SKY-165050-152548 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1234 ------------------------------------------------------------------------------------------------------------------------------------