Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5221 Report Date: 18-Jul-95:17:05 Version: ********** Check-in Date: ********** 1.Proposal Title: THE VERTICAL STRUCTURE OF THE ATMOSPHERE OF NEPTUNE ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SOLAR SYSTEM GTO/WF2 Target of Oppt. Sub Category OUTER PLANETS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. John T. Trauger 2370 USA (818)354-9594 PROJECT SCIENTIST ------------------------------------------------------------------------------------ 7. Abstract We propose to use WF/PC-II to make synoptic-scale observations of the atmosphere of Neptune. These observations will employ the new capabilities the WF/PC-II to place more stringent constraints on the composition and the vertical structure of the clouds and hazes above the main cloud deck. They will also help to resolve the nature, longevity, and dynamics of the great dark spot (GDS), the bright streaks and other large-scale features observed by during the Voyager Neptune encounter. ------------------------------------------------------------------------------------ 8. Scientific Key Words: NEPTUNE; ATMOSPHERE ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 3.55 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5221 PI: Dr. John T. Trauger Proposal Title: THE VERTICAL STRUCTURE OF THE ATMOSPHERE OF NEPTUNE ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ John T. Trauger Con David Crisp 2370 USA Con John T. Clarke 2660 USA Chris Burrows STSCI USA John Hoessel UNIV. OF WISCONSIN USA Jay Gallagher UNIV. OF WISCONSIN USA Richard Griffiths JOHNS HOPKINS UNIV USA Jeff Hester ARIZONA STATE UNIV. USA John Holtzman LOWELL OBSERVATORY USA Jeremy Mould CALTECH USA James Westphal CALTECH USA Page 3 ------------------------------------------------------------------------------------ 3. Description of proposed observations. Cycle-4 Vertical Structure/Cloud Composition Experiment: Full-disk PC images of one hemisphere of Neptune will be taken in broad-band UV filters (F218W, F225W, F300W), and a series of visible and near-infrared filters (F467M, F588N, F673N, QFCH4Nb, QFCH4Nd) to constrain the vertical distribution of aerosols and methane gas above the main cloud tops. The opposite hemisphere will be observed with only a subset of these filters (F300W, F467M, F588N, F673N, QFCH4Nb) during this cycle. We will use center-to-limb observations of rayleigh scattering at UV and blue wavelengths to determine the relative altitudes of the GDS, the bright companions, and other cloud features that are visible on Neptune's disk. These observations will also be combined with methane-quad observations to provide improved constraints on the composition, optical depth, and size distribution of the high-altitude stratospheric aerosols. Finally, full-disk PC observations with the methane quad (QFCH4Nb, and QFCH4Nd) will be combined with ground-based observations of thermal emission (cf. Orton et al. 1988) to help determine the vertical distribution of methane gas above the main cloud deck. If we observe bright cloud features on Neptune, this methane gas data will be used along with the altitude data obtained in the vertical structure experiment to determine if these bright cloud streaks are composed of methane ice. Neptune is a 7th magnitude object with a 2.3" disk and a 16 to 20-hour atmospheric rotation period (~20 degrees/hr). A cloud feature at the sub-Earth point on Neptune therefore moves about 1 PC pixel (0.04 arcsec) in 350 seconds. At least four 350-second exposures will be needed to yield adequate S/N in the in the UV filters and in the QFCH4Nd filter. The first filter sequence includes a total of 17 exposures (including CR-splits) on the first hemisphere. The second sequence on the other hemisphere includes 5 exposure. The filters and their optimum exposure times are itemized in the following table: ------------------------------------------------ ----------------------- Table 1: Neptune Filters and Optimal Exposure Times: The following table lists the exposure times, S/N, and estimated flux for each of the filters in the Neptune program. All flux values are expressed in erg/s/cm^2/arcsec^2/Angstrom. These values are uncertain by about a factor of 2. Camera Filter and flux S/N exposure wavelength(A) erg/s/cm^2/arcsec^2/A time (sec) PC f218w 2.1e-14 16 350.0 PC *f255w 4.1e-14 30 350.0 PC f300w 2.2e-13 100 176.0 PC f467m 8.9e-13 100 45.0 PC f588n 6.6e-13 100 72.0 PC qfch4n_b (626.5nm) 3.2e-13 92 350.0 PC f673n 2.4e-14 70 176.0 PC qfch4n_d (894.0nm) 1.2e-14 28 350.0 * This filter was not included in our Phase-1 proposal, and is not "protected", but was added to the sequence to facilitate comparisons with the 260 nm observations acquired by the Voyager Photopolarimeter. ............... The atmosphere of Neptune rotates rapidly (16 - 20 hour period), and different latitudes rotate at slightly different rates. The exposure sequence must therefore be chosen carefully to observe a similar range of longitudes in all filters. A maximum of 5 350-sec exposures can be taken during the usable part of each HST orbit (~33 minutes). During this period, the planet will rotate about 10 degrees (~2 PC pixels at sub-Earth angles near 60 degrees, < 1 PC pixel at sub-Earth angles > 80 degrees). These motions are small enough to allow the mapping of images acquired in different filters to a common latitude-longitude grid for comparison. Parts of 4 successive HST orbits will be needed to acquire all images in the first sequence. These exposures cannot be obtained on adjacent orbits, however because the planet rotates too much between orbits to allow registration of the images. Instead, each orbit in the first image sequence should be separated by approximately 18 hours (12 orbits) so that they observe the same face of Neptune. All images in the second sequence can be taken in a single orbit, but this sequence must be initiated approximately 9 hours after the start of the first sequence to observe the opposite hemisphere of Neptune. Page 4 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. This program will take advantage of several new features of WF/PC-II, including the improved UV performance, and the new UV and narrowband-Vis filter set. The high spatial resolution provided by the HST WF/PC-II is a vital asset to this program because the size of Neptune's disk never exceeds 2.3 arc-seconds. The photometric accuracy offered by WF/PC-II is also required to resolve the vertical distribution of the clouds and aerosols from studies of center-to-limb contrast variations. Finally, the freedom from telluric atmospheric absorption is important for the UV observations, which are essential for determining the composition and vertical distribution of the stratospheric aerosols. Because Neptune is a relatively bright object, and because its atmosphere rotates rapidly (~16-20 hour period), each exposure is limited to 350 seconds. Up to 4 exposures must be co-added to provide the S/N needed for some filters used here. Two observation periods, initiated 9 hours apart are needed to both hemispheres of the planet. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. Neptune is best observed in July of 1994 or 1995, when it is near opposition, and its angular size is greatest (2.3 arc seconds). Each sequence of exposures should be acquired as rapidly as possible so that they show the same face of Neptune. 4 HST orbits will be needed to acquire all images in sequences 1 and 2. These exposures cannot be obtained on adjacent orbits, however because the planet rotates too much between orbits to allow registration of the images. Instead, each orbit in the first image sequence should be separated by approximately 18 hours (12 orbits) so that they observe the same face of Neptune. All images in the second sequence can be taken in a single orbit, but this sequence must be initiated approximately 9 hours after the start of the first sequence to observe the opposite hemisphere. ------------------------------------------------------------------------------------ 11. Address Information Name: JOHN T. TRAUGER Category: PI Institution: 2370 Address: 4800 OAK GROVE DRIVE MAIL STOP 179-225 City: PASADENA State: CA Zip Code: 91109 Country: USA Telephone: (818) 354-9594 Telex (or e-mail): 67-5429 ------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5221 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: NEPTUNE ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET NEPTUNE ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = NEPTUNE | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | WND1 = 12-MAY-1994 TO | 12-SEP-1994, WND2 = | 12-MAY-1995 TO | 12-SEP-1995 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 9.45 | OBSERVATIONS TAKEN AS NEAR POSSIBLE 2 |F(2250) = 4.1 E-14 | TO JULY 12, 1994 OPPOSITION. USE 3 |F(3000) = 2.2 E-13 | 1995 WINDOW ONLY IN THE CASE OF 4 |F(4670) = 8.9 E-13 | SUBSTANTIAL LAUNCH DELAY. 5 |F(5880) = 6.6 E-13 | 6 |F(6265) = 3.2 E-13 | 7 |F(6730) = 2.4 E-14 | 8 |F(8940) = 1.2 E-14 | 9 |SIZE = 2.3 | 10 |F(2180) = 2.1 E-14 | | ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5221 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1.1 DEFINE NEPTUNE WFPC2 IMAGE PC1 F218W CR-SPLIT=NO 4 300S 16 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 350S 10 E1 Comments: OBSERVATIONS SHOULD BE MADE AS CLOSE AS POSSIBLE TO JULY 12, 1994. OBSERVE AT JULY 1995 OPPOSITION ONLY IN THE CASE OF A SUBSTANTIAL LAUNCH DELAY. ------------------------------------------------------------------------------------------------------------------------------------ 2.1 DEFINE NEPTUNE WFPC2 IMAGE PC1 F255W CR-SPLIT=NO 2 260S 30 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 350S 2 E2 ------------------------------------------------------------------------------------------------------------------------------------ 2.2 DEFINE NEPTUNE WFPC2 IMAGE FQCH4P1 FQCH4P15 8922 CR-SPLIT=NO 2 260s 28 1 1 PCS MODE F NEPIMAG 5 ATD-GAIN=7 350S 8 E2 ------------------------------------------------------------------------------------------------------------------------------------ 3.1 DEFINE NEPTUNE WFPC2 IMAGE PC1 F300W CR-SPLIT=NO 1 180S 100 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 176S 3 E3 ------------------------------------------------------------------------------------------------------------------------------------ 3.2 DEFINE NEPTUNE WFPC2 IMAGE PC1 F467M CR-SPLIT=NO 1 40S 100 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 45S 4 E3 ------------------------------------------------------------------------------------------------------------------------------------ 3.3 DEFINE NEPTUNE WFPC2 IMAGE PC1 F588N CR-SPLIT=NO 1 70S 100 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 72S 5 E3 ------------------------------------------------------------------------------------------------------------------------------------ 3.4 DEFINE NEPTUNE WFPC2 IMAGE FQCH4N1 FQCH4N15 6193 CR-SPLIT=NO 1 350S 92 1 1 PCS MODE F NEPIMAG 5 ATD-GAIN=7 350S 6 E3 ------------------------------------------------------------------------------------------------------------------------------------ 3.5 DEFINE NEPTUNE WFPC2 IMAGE PC1 F673N CR-SPLIT=NO 1 180S 70 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 176S 7 E3 ------------------------------------------------------------------------------------------------------------------------------------ 4.1 DEFINE NEPTUNE WFPC2 IMAGE PC1 F300W CR-SPLIT=NO 1 180S 100 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 176S 3 E4 ------------------------------------------------------------------------------------------------------------------------------------ 4.2 DEFINE NEPTUNE WFPC2 IMAGE PC1 F467M CR-SPLIT=NO 1 40S 100 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 45S 4 E4 ------------------------------------------------------------------------------------------------------------------------------------ 4.3 DEFINE NEPTUNE WFPC2 IMAGE FQCH4P1 FQCH4P15 8922 CR-SPLIT=0.5 1 700S 28 1 1 PCS MODE F NEPIMAG 5 ATD-GAIN=7 350S 8 E4 ------------------------------------------------------------------------------------------------------------------------------------ 5.1 DEFINE NEPTUNE WFPC2 IMAGE PC1 F588N CR-SPLIT=NO 1 70S 100 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 72S 5 E5 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5221 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 5.2 DEFINE NEPTUNE WFPC2 IMAGE FQCH4N1 FQCH4N15 6193 CR-SPLIT=NO 1 350S 92 1 1 PCS MODE F NEPIMAG 5 ATD-GAIN=7 350S 6 E5 ------------------------------------------------------------------------------------------------------------------------------------ 5.3 DEFINE NEPTUNE WFPC2 IMAGE PC1 F673N CR-SPLIT=NO 1 180S 70 1 1 PCS MODE F NEPIMAG ATD-GAIN=7 176S 7 E5 ------------------------------------------------------------------------------------------------------------------------------------ 10 USE CYCLE 4 NEPIMAG AT 12-JUL-94 +/- E1 60D Comments: OBSERVATIONS SHOULD BE MADE AS CLOSE AS POSSIBLE TO JULY 12, 1994 ------------------------------------------------------------------------------------------------------------------------------------ 20 USE SEQ 2.1-2.2 NO GAP NEPIMAG CYCLE 4 E2 AFTER 10 BY 18H +/ -0.8H ------------------------------------------------------------------------------------------------------------------------------------ 30 USE SEQ 3.1-3.5 NO GAP NEPIMAG CYCLE 4 E3 AFTER 10 BY 36H +/ -0.8H ------------------------------------------------------------------------------------------------------------------------------------ 40 USE SEQ 4.1-4.3 NO GAP NEPIMAG CYCLE 4 E4 AFTER 10 BY 9.3H + /-0.8H Comments: COULD BEGIN 27.3H AFTER 10 ------------------------------------------------------------------------------------------------------------------------------------ 50 USE SEQ 5.1-5.3 NO GAP NEPIMAG CYCLE 4 E5 AFTER 10 BY 27.3H +/-0.8H Comments: SHOULD BEGIN 18H AFTER 40 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5221 [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ATD-GAIN=7 CR-SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GTO/WF2 ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 3.55 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category OUTER PLANETS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F CYCLE 4; AT 12-JUL-94 +/- 60D; SEQ 2.1-2.2 NO GAP; AFTER 10 BY 18H +/-0.8H SEQ 3.1-3.5 NO GAP; AFTER 10 BY 36H +/-0.8H SEQ 4.1-4.3 NO GAP; AFTER 10 BY 9.3H +/-0.8H SEQ 5.1-5.3 NO GAP; AFTER 10 BY 27.3H +/-0.8H ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F218W F255W FQCH4P15 F300W F467M F588N FQCH4N15 F673N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NEPTUNE ------------------------------------------------------------------------------------------------------------------------------------