Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5312 Report Date: 18-Jul-95:17:08 Version: ********** Check-in Date: ********** 1.Proposal Title: A DEEP IMAGING SEARCH FOR THE SOURCE OF THE SHORT PERIOD COMETS: CYCLE 4 HIGH ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SOLAR SYSTEM GO Sub Category COMETS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Anita L. Cochran 3550 USA 512-471-1471 ------------------------------------------------------------------------------------ 7. Abstract We propose to perform a deep WFPC2 imaging search for the Kuiper Belt, the probable source of the short period comets. The search will consist of two sets of thirty 10 -min exposures. Each set (total exposure time for each is 5-hour) will reach a limiting magnitude of 28.5, or down to objects of radius = 11 km if they have albedo = 0.04 and are at 40 AU. The search will be complete down to this size. If reasonable assumptions are made about initial surface density distribution, albedo and minimum size of a body which could be seen as a short period comet, we would expect to see between 12 and 65 Kuiper belt objects. This is in marked contrast to ground-based studies which are limited to relatively large objects (radius > 55 km) which are atypical of short period comets. Whereas the ground-based searches have proved the existence of bodies in the region of the Kuiper belt, they are unable to prove the belt contains objects that are the size of short period comets, nor can they define the size distribution. The HST survey we propose will either confirm the link between short period comets and the Kuiper belt, or it will place severe constraints on the size distribution of objects in the belt. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 10.00 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5312 PI: Anita L. Cochran Proposal Title: A DEEP IMAGING SEARCH FOR THE SOURCE OF THE SHORT PERIOD COMETS: CYCLE 4 HIGH ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Anita L. Cochran 3550 USA Martin J. Duncan 3440 USA Harold F, Levison 3440 USA Sol A. Stern 3440 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We propose 2 sets of observations with WFPC2. Each set of WFPC2 observations consists of thirty 10-min integration ``Wide V'' (F606W) frames which total to 5- hours total integration per set. Each individual 5-hour set needs to be collected in a single 24-hour period. There should be no spacecraft roll between frames in a set of observations. We will collect data with all three WF chips and the PC chip. The combined field of view is 5.3 arcmin**2. The fields to be imaged consist of fields along the ecliptic but not within 20 deg of the galactic plane. Fields will be chosen to be of dark clouds to minimize the number of background stars. We have a list of two dozen such fields spread over 24 hours of RA. We specify here one such field which was chosen because of its good position and blankness. We propose to observe this field twice, 6 months apart, at quadrature. This is our preferred field but we can supply coordinates of any of the other fields on our list in the event that it is not possible to obtain the observations of this particular field. This program should be run in fine lock. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Objects in the Kuiper belt are expected to have albedos of a few percent. With an inner distance of the belt of 40 au, objects should be quite faint. Several ground-based searches have been performed with limiting magnitudes up to m=25. Objects of this magnitude at 40 au and 4% albedo would have radii of 55km. It is not expected that ground-based searches can reach fainter limiting magnitudes for moving objects in the foreseeable future because they are limited by sky brightness and seeing. Indeed, even the Keck telescope will suffer from sky- brightness limits which will dominate the signal of these faint objects. Additionally, very long observations of moving objects suffer from confusion limits due to motion of the object resulting in substantial star trails. Still, ground-based searches DID find 2 objects with radii ~100km. Most SPCs are much smaller than 55km so, in order to search for progenitors of the typical SPC, it is necessary to push the limiting magnitudes down as far as possible, but to do this with integrations which don't span such a long time that objects disappear from the field of view. This last constraint makes an orbiting telescope necessary. HST is the only orbiting telescope with deep-sky imaging capabilities. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We require that there be no roll during or between 10-min exposures for each 30- exposure set. This is necessary so that we can co-register the images to reach our deep limiting magnitude. We also require that each complete set of thirty 10- min exposures be completed within a 24-hour period. The objects will be moving 5 -6 pixels/hour so in a 24-hour period they will move 120-144 pixels. This will result in objects being lost in some of the 10-min exposures. However, even in 24 -hours, at most 7% of the Kuiper belt field would suffer from decreased S/N. We would prefer if the observations could be completed in the minimum possible time, allowing for earth occultations and guide star reacquisitions. Page 3 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. No special calibrations required. Normal flat fields will be sufficient. We will also use the standard calibration standard area for approximate photometry. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. NONE ------------------------------------------------------------------------------------ 9. Description of previous HST work. Cycle 1: P4024 High Resolution UV Spectroscopy of Triton (Stern, PI); Cycle 1: P2560 UV Rotational Light Curves of Pluto, and Charon's UV Spectrum (Stern, CoI); Cycle 2: P3803 CO Abundance and FUV Survey (Stern, CoI). Cycle 2: P4005 Observations of Jovian Aurora in Support of Ulysses (Stern, PI); Cycle 3: P4462 Deep UV Spectroscopy of Triton (Stern, CoI); None of the above programs are related to this proposal. To date, the Pluto observations have not been completed. However, the final Triton Cycle 1 (P4024) FOS data were obtained in May 1992, and have now been analyzed (Stern et al. 1993). This spectrum was made at a different orbital longitude (and therefore rotational epoch) than the IUE data, and has been compared to the reduced IUE spectra. It (i) confirms that Triton's UV lightcurve amplitude is higher than in any of the Voyager color filters, (ii) shows that Triton's UV color slope varies with rotational aspect, and (iii) most importantly, reveals a suite of complex absorption features not detectable in previous, IUE studies. Our Cycle 3 Triton program, which will make more detailed studies of Triton's UV spectrum, has not yet been carried out. The Jupiter program (GO P4005) yielded eight FOC F130M/F145W images of the aurora of Jupiter taken in conjunction with the flyby of the Ulysses spacecraft in 1992. We have reduced and analyzed these images. Results were presented at a workshop in 1992 (Waite et al. 1992) and are now being prepared for publication (Waite, Stern et al. 1993). The images clearly demonstrate that the spatial morphology of the Jovian aurora are significantly more complex than IUE-investigators were led to believe. Papers Published: "HST Ultraviolet Spectroscopy of Triton: Evidence for Complex Surface Absorbers", Stern, S. A., L. M. Trafton, and D. Cruikshank. Astrophysical J. Lett. Submitted, 1993. "Multispectral Observations of the Jupiter Aurora", Waite, J. H., M. McGrath, L.M. Trafton, S. A. Stern, and G. R. Gladstone Proc. International Workshop on Time Variable Phenomena in the Jovian Planetary System, Annapolis, Md. July 13-16, 1992. "HST and ROSAT Images of the Jovian Aurora: A New Paradigm?", Waite, J. H., S. A. Stern, F. Bagenal, M. McGrath, L. M. Trafton, and G. R. Gladstone. JGR In preparation, 1993. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). The nominal data reduction will be performed on a SPARCStation 10 model 41 which was obtained from NASA Planetary Astronomy funds and is currently on-site and operational at The University of Texas. The software to perform the reduction will be the IRAF and STSDAS packages. These packages are installed and operational and fully supported by staff at The University of Texas. The search for moving objects will be performed independently at two sites, The University of Texas and Southwest Research Institute (SwRI). The equipment used at The University of Texas is described above. SwRI will supply a SPARCStation IPC for this purpose. This workstation was purchased through internal capital equipment funds. Modeling of the Kuiper belt will be performed on an HP9000 model 735 and an HP9000 model 720 at SwRI. These workstations were purchased through internal capital equipment funds. SwRI will not charge overhead on travel. ------------------------------------------------------------------------------------ 11. Address Information Page 4 Name: ANITA L. COCHRAN Category: PI Institution: 3550 Address: DEPARTMENT OF ASTRONOMY UNIVERISITY OF TEXAS City: AUSTIN State: TX Zip Code: 78712 Country: USA Telephone: 512-471-1471 Telex (or e-mail): 512-471-6016 ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5312 [ 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 FIELD- G,505 RA = 03H 41M 20.0S +/- 2000 1 V=26.5+/-2.0 034120+19344 0.25S, 1 B-V=0.7 1 DEC = +019D 34' 41" +/- 03" Comments: TARGET IS A DARK CLOUD BORDERING BETWEEN PISCES & ARIES, ESSENTIALLY ON THE ECLIPTIC. WE ARE USING THIS DARK CLOUD AS A SUITABLE BACKGROUND TO SEARCH FOR OBJECTS IN THE THIN, ECLIPTIC-CENTERED KUIPER COMET BELT ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5312 [ 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 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 30M 4 1 1 CYCLE 4 /1-2.8 034120+1934 FIX 300M PCS MODE F / 1-2.8 41 POS TARG -28.7, 10.3 /1.0-1.8 SAME ORIENT FOR 1.1-1.8 AS 1.0 Comments: 1) ROLL ORIENTATION MUST BE SEQ 1.0-1.8 within FIXED FOR THE 30 EXPOSURES. WE 24h TAKE DATA IN ALL 4 WFPC2 CHIPS. ALL 30 OF THE 10M EXPOSURES SHOULD OCCUR IN THE MINIMUM TIME, AND MUST OCCUR IN <24 TO FINISH. AT 20-AUG-94+/-3D ------------------------------------------------------------------------------------------------------------------------------------ 1.1 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 1 034120+1934 FIX 300M 41 Comments: ORBIT 2 ------------------------------------------------------------------------------------------------------------------------------------ 1.2 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 1 034120+1934 FIX 300M 41 Comments: ORBIT 3 ------------------------------------------------------------------------------------------------------------------------------------ 1.3 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 1 034120+1934 FIX 300M 41 Comments: ORBIT 4 ------------------------------------------------------------------------------------------------------------------------------------ 1.4 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 30M 4 1 1 034120+1934 FIX 300M 41 Comments: ORBIT 5 ------------------------------------------------------------------------------------------------------------------------------------ 1.5 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 1 034120+1934 FIX 300M 41 Comments: ORBIT 6 ------------------------------------------------------------------------------------------------------------------------------------ 1.6 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 1 034120+1934 FIX 300M 41 Comments: ORBIT 7 ------------------------------------------------------------------------------------------------------------------------------------ 1.7 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 1 034120+1934 FIX 300M 41 Comments: ORBIT 8 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5312 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1.8 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 1 034120+1934 FIX 300M 41 Comments: ORBIT 9 ------------------------------------------------------------------------------------------------------------------------------------ 2 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 30M 4 1 2 ORIENT 180D +/- 0D 034120+1934 FIX 300M FROM 1.000 41 POS TARG -28.7, 10.3 /2.000 SAME ORIENT FOR 2.1-2.8 AS 2.0 Comments: 1) ROLL ORIENTATION MUST BE SEQ 2.0-2.8 within FIXED FOR THE 30 EXPOSURES. WE 24h TAKE DATA IN ALL 4 WFPC2 CHIPS. ALL 30 OF THE 10M EXPOSURES SHOULD OCCUR IN THE MINIMUM TIME, AND MUST OCCUR IN <24 TO FINISH. AT 16-FEB-95+/-3D ------------------------------------------------------------------------------------------------------------------------------------ 2.1 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 2 034120+1934 FIX 300M 41 Comments: ORBIT 2 ------------------------------------------------------------------------------------------------------------------------------------ 2.2 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 2 034120+1934 FIX 300M 41 Comments: ORBIT 3 ------------------------------------------------------------------------------------------------------------------------------------ 2.3 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 2 034120+1934 FIX 300M 41 Comments: ORBIT 4 ------------------------------------------------------------------------------------------------------------------------------------ 2.4 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 30M 4 1 2 034120+1934 FIX 300M 41 Comments: ORBIT 5 ------------------------------------------------------------------------------------------------------------------------------------ 2.5 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 2 034120+1934 FIX 300M 41 Comments: ORBIT 6 ------------------------------------------------------------------------------------------------------------------------------------ 2.6 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 2 034120+1934 FIX 300M 41 Comments: ORBIT 7 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5312 [ 8] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 2.7 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 2 034120+1934 FIX 300M 41 Comments: ORBIT 8 ------------------------------------------------------------------------------------------------------------------------------------ 2.8 FIELD- WFPC2 IMAGE WFALL- F606W CLOCKS=YES 1 34M 4 1 2 034120+1934 FIX 300M 41 Comments: ORBIT 9 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5312 [ 9] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 10.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category COMETS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4 /1-2.8; PCS MODE F / 1-2.8; POS TARG -28.7, 10.3 /1.0-1.8; SAME ORIENT FOR 1.1-1.8 AS 1.0; SEQ 1.0-1.8 within 24h; ORIENT 180D +/- 0D FROM 1.000; POS TARG -28.7, 10.3 /2.000; SAME ORIENT FOR 2.1-2.8 AS 2.0; SEQ 2.0-2.8 within 24h; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names FIELD-034120+193441 ------------------------------------------------------------------------------------------------------------------------------------