Proposal_Information
Title: Clouds and Aerosols on Saturn and Uranus
Proposal_Category: GO
Scientific_Category: Solar System
Cycle: 5
Investigators
PI_name: Dr. Martin Tomasko
PI_Institution: Lunar and Planetary Lab
CoI_Name: Dr. Erich Karkoschka
CoI_Institution: Lunar and Planetary Lab
Contact: N
Abstract:
Our goal is to determine the vertical and horizontal
distributions, and the optical and microphysical properties,
of aerosols and clouds in the atmospheres of the outer
planets. This information is needed to understand the roles
of aerosols in forcing atmospheric circulation and particle
microphysics. To achieve these goals we propose to acquire
WFPC2 images of Saturn and Uranus in the UV, visible, and near
-IR methane and continuum regions. UV and blue images provide
vertical sounding of the absorptive part of the aerosol
opacity, critical for heat-balance studies, while the methane
bands give information on the scattering part. The
combination of the two provides an estimate of particle size
from the wavelength dependence of the opacity. HST
observations are critical because (1) UV images can only be
obtained by HST, (2) the high resolution provided by HST is
required for center-to-limb coverage, and (3) of existing
space observations, only HST provides a suitable wide range of
filters. Observations taken during Saturn's ring-plane
crossing in 1995 permit superior imaging of both hemispheres,
especially in methane bands. New observations of Uranus can
take advantage of the improved geometry for center-to-limb
observations. This proposal is similar to one originally
selected for Cycle 1 (program number 2564) for the outer
planets that had to be limited to Jupiter and Saturn due to
the degraded performance of the original HST optics.
Questions
Observing_Description:
Our analyses requires a series of images in continuum and
methane band filters. We need three methane band filters:
FQCH4N15 (619 nm), FQCH4N (727 nm), and FQCH4P15 (892 nm).
For Uranus, we use four continuum filters: F336W, F467M,
F673N, and F850LP (which gets most of its light from the
940 nm continuum region). For Saturn we also use the
continuum filters F255W, F410M, and F588N, and we replace
the F850LP by the F953N filter. The most important filters
are repeated for Saturn, since Saturn shows some changes
with time and longitude. For most of the filters we
achieve 70 per cent of the saturation level with relatively
short exposure times. For those exposures, the maximum
exposure time is set equal to the desired exposure time,
so they will not be lengthened in case more time is
available as described in the Phase II Proposal Instructions.
A few exposures are not close to saturation as indicated
by a longer maximum duration.
Saturn's rings fit into the PC1 aperture only for some
orientations. The optimal orientation is described in
the visit requirements. Because of the asymmetric field of
view of the 892 nm methane filter, we specify an offset
from the centered position (POS TARG). The offset for both
of the orbits of visit #3 is slightly different so that
CCD blemishes will not fall on the same area.
Real_Time_Justification:
Our long exposures on Saturn in the strongest methane bands
require the rings to be dark in order not to saturate the
image. The earth-facing side of the rings is not illuminated
from 22 May 1995 to 11 August 1995 and from 19 November 1995
to 12 February 1996. Additionally, starting near 10 November
1995, the solar illumination will be so shallow that the
rings will be faint enough.
We want to observe two interesting phases of the ring-plane
crossings of this season. In visit #2, the sun will shine
through the transparant rings yielding scattering information
about the rings at higher spatial resolution than possible
from the ground. In visit #3, the sun will illuminate the
rings at an angle of 0.03 degrees, giving a very sensitive
probe of non-planar ring features. Voyager observed some
bending waves when the sun was illuminating the rings at an
angle of a few degrees. The extremly shallow illumination
on 18/19 November 1995 has prospects for discoveries of
ring features. If we miss this opportunity, the next one
will be on 24 January 2039.
In October, 1994, HST observations yielded the first map
of Titan's surface. With proper scheduling, our Saturn
observations could be made when Titan is in the field.
Our filter set is more complete than the filter used on
Titan so far. Our F953N filter may probe the surface
better than the F850LP filter which showed surface features
of highest contrast so far. On the other hand, we have
a poor orbital coverage with only two positions if the
observation can be scheduled according to our visit requests.
Thus, our data set would be complementary to the existing one.
We will conduct spectrophotometry of Saturn and Uranus
at the 1.5 m spectroscopic telescope at the European
Southern Observatory on 6-10 July 1995.
These observations will provide spectroscopic information
at 1 nm resolution with relatively low spatial resolution,
while the HST images will provide high spatial resolution
at a few wavelengths sampling the spectrum. Such
supplemental data sets have been proven to be very valuable
in the past. For example, HST filter transmission curves can
be convolved with the planetary spectrum for an accurate
interpretation of the HST images. We prefer if one or
two of our visits can be scheduled in July, 1995.
Solar_System_Targets
Target_Number: 1
Target_Name: URANUS
Description: PLANET URANUS
Level_1: STD = URANUS
Window: OLG OF URANUS BETWEEN 300 60
Flux: V = 5.6
B-V = 0.6
U-B = 0.3
Comments: Window requirement means within 2 months of opposition.
Target_Number: 2
Target_Name: SATURN-NO-RING
Description: PLANET SATURN
Level_1: STD = SATURN
Window: WND FROM 22-MAY-95 TO 11-AUG-95
WND FROM 10-NOV-95 TO 11-FEB-96
OLG OF TITAN BETWEEN 174 183
SEP OF TITAN SATURN FROM EARTH GT .5"
Flux: V = 1.1
B-V = 1.1
U-B = 0.6
Comments: The WND requirement is the time period when Saturn's
rings are so dark that they will not saturate in
methane filter exposures. This is essential as
described in the proposal.
We request Titan in the field of view (orbital
longitude 174-183 degrees). This is not a requirement.
Target_Number: 3
Target_Name: SATURN-DIM-RING
Description: PLANET SATURN
Level_1: STD = SATURN
Window: WND FROM 22-MAY-95 TO 11-AUG-95
WND FROM 10-NOV-95 TO 11-FEB-96
Flux: V = 1.1
B-V = 1.1
U-B = 0.6
Comments: The WND requirement is the time period when Saturn's
rings are so dark that they will not saturate in
methane filter exposures. This is essential as
described in the proposal.
Visits
Visit_Number: 1
Visit_Requirements: BEFORE 25-JUL-95
Visit_Comments: We request that this visit occurs within a few weeks
of our observing run at the European Southern
Observatory 6-10 July 1995 where we will aquire
spectroscopic data of Uranus.
In case of scheduling difficulties, the BEFORE
request can be deleted.
Exposure_Number: 11
Target_Name: URANUS
Config: WFPC2
Opmode: IMAGE
Aperture: FQCH4W4
Sp_Element: F467M
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 8S
Special_Requirements: MAX DUR 8S
Exposure_Number: 12
Target_Name: URANUS
Config: WFPC2
Opmode: IMAGE
Aperture: FQCH4W4
Sp_Element: FQCH4N
Wavelength: 7274
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 160S
Special_Requirements: MAX DUR 180S
Exposure_Number: 13
Target_Name: URANUS
Config: WFPC2
Opmode: IMAGE
Aperture: FQCH4P15
Sp_Element: F336W
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 100S
Special_Requirements: MAX DUR 120S
Exposure_Number: 14
Target_Name: URANUS
Config: WFPC2
Opmode: IMAGE
Aperture: FQCH4P15
Sp_Element: FQCH4N15
Wavelength: 6211
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 160S
Special_Requirements: MAX DUR 230S
Exposure_Number: 15
Target_Name: URANUS
Config: WFPC2
Opmode: IMAGE
Aperture: FQCH4P15
Sp_Element: F673N
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 100S
Special_Requirements: MAX DUR 100S
Exposure_Number: 16
Target_Name: URANUS
Config: WFPC2
Opmode: IMAGE
Aperture: FQCH4P15
Sp_Element: F850LP
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 100S
Special_Requirements: MAX DUR 120S
Exposure_Number: 17
Target_Name: URANUS
Config: WFPC2
Opmode: IMAGE
Aperture: FQCH4P15
Sp_Element: FQCH4P15
Wavelength: 8922
Optional_Parameters: ATD-GAIN=7
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 500S
Special_Requirements: MAX DUR 1500S
Visit_Number: 2
Visit_Requirements: ORIENT 272D TO 276D
BEFORE 12-AUG-95
Visit_Comments: We request a position angle of the X-axis of the
WFPC2 of 229 degrees within a few degrees. This
orientation optimizes the location of Saturn's
rings on the CCD.
We request that this visit occurs within the
first dark-ring period since we obtain
spectroscopic data of Saturn at the European
Southern Observatory during this period
(6-10 July 1995). This is not a requirement.
Exposure_Number: 21
Target_Name: SATURN-NO-RING
Config: WFPC2
Opmode: IMAGE
Aperture: WF4-FIX
Sp_Element: F255W
Optional_Parameters: ATD-GAIN=7
Number_of_Iterations: 1
Time_Per_Exposure: 160S
Special_Requirements: MAX DUR 300S
POS TARG 13,-17
Exposure_Number: 22
Target_Name: SATURN-NO-RING
Config: WFPC2
Opmode: IMAGE
Aperture: WF4-FIX
Sp_Element: FQCH4N
Wavelength: 7274
Optional_Parameters: ATD-GAIN=15
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 12S
Special_Requirements: MAX DUR 12S
POS TARG 13,-17
Exposure_Number: 23
Target_Name: SATURN-NO-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F336W
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 70S
Special_Requirements: MAX DUR 70S
POS TARG -2,-1
Exposure_Number: 24
Target_Name: SATURN-NO-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F467M
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 16S
Special_Requirements: MAX DUR 16S
POS TARG -2,-1
Exposure_Number: 25
Target_Name: SATURN-NO-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: FQCH4N15
Wavelength: 6211
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 30S
Special_Requirements: MAX DUR 30S
POS TARG -2,-1
Exposure_Number: 26
Target_Name: SATURN-NO-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F673N
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 18S
Special_Requirements: MAX DUR 18S
POS TARG -2,-1
Exposure_Number: 27
Target_Name: SATURN-NO-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F953N
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 100S
Special_Requirements: MAX DUR 120S
POS TARG -2,-1
Exposure_Number: 28
Target_Name: SATURN-NO-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: FQCH4P15
Wavelength: 8922
Optional_Parameters: ATD-GAIN=15
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 500S
Special_Requirements: MAX DUR 700S
POS TARG -2,-1
Visit_Number: 3
Visit_Requirements: ORIENT 92D TO 96D
BETWEEN 16-NOV-95:20:00 AND 17-NOV-95:13:00
Visit_Comments: We request a position angle of the X-axis of the
WFPC2 of 49 degrees within a few degrees. This
orientation optimizes the location of Saturn's
rings on the CCD.
We request that this visit occurs at the beginning
of the crossing of the solar disk through the ring
plane of Saturn, yielding an extremely shallow
illumination which makes non-planar ring features
visible. The next day such a geometry is observable
to HST is on 24 January 2039. In case of
scheduling difficulties the start time of the
requested period could be shifted half a day or
one day later, which still would yield a quite
shallow illumination.
Exposure_Number: 31
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F673N
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 18S
Special_Requirements: MAX DUR 18S
POS TARG -2,-2
Exposure_Number: 32
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F953N
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 100S
Special_Requirements: MAX DUR 120S
POS TARG -2,-2
Exposure_Number: 33
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: FQCH4P15
Wavelength: 8922
Optional_Parameters: ATD-GAIN=15
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 400S
Special_Requirements: MAX DUR 1200S
POS TARG -2,-2
Exposure_Number: 34
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: FQCH4P15
Wavelength: 8922
Optional_Parameters: ATD-GAIN=15
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 300S
Special_Requirements: MAX DUR 400S
POS TARG -2,-2
Exposure_Number: 35
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: WF4-FIX
Sp_Element: FQCH4N
Wavelength: 7274
Optional_Parameters: ATD-GAIN=15
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 23S
Special_Requirements: MAX DUR 23S
POS TARG 13,-17
Exposure_Number: 36
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: WF4-FIX
Sp_Element: FQCH4N
Wavelength: 7274
Optional_Parameters: ATD-GAIN=15
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 10S
Special_Requirements: MAX DUR 10S
POS TARG 13,-17
Exposure_Number: 37
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: WF4-FIX
Sp_Element: F255W
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 350S
Special_Requirements: MAX DUR 350S
POS TARG 13,-17
Exposure_Number: 41
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F336W
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 80S
Special_Requirements: MAX DUR 80S
POS TARG -2,-1
Exposure_Number: 42
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F410M
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 40S
Special_Requirements: MAX DUR 60S
POS TARG -2,-1
Exposure_Number: 43
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F467M
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 18S
Special_Requirements: MAX DUR 18S
POS TARG -2,-1
Exposure_Number: 44
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F588N
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 14S
Special_Requirements: MAX DUR 14S
POS TARG -2,-1
Exposure_Number: 45
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: FQCH4N15
Wavelength: 6211
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 30S
Special_Requirements: MAX DUR 30S
POS TARG -2,-1
Exposure_Number: 46
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F673N
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 18S
Special_Requirements: MAX DUR 18S
POS TARG -2,-1
Exposure_Number: 47
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: F953N
Optional_Parameters: ATD-GAIN=15
Number_of_Iterations: 1
Time_Per_Exposure: 100S
Special_Requirements: MAX DUR 120S
POS TARG -2,-1
Exposure_Number: 48
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: FQCH4P15
Wavelength: 8922
Optional_Parameters: ATD-GAIN=15
CR-SPLIT=NO
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 700S
Special_Requirements: MAX DUR 1200S
POS TARG -2,-1
Exposure_Number: 49
Target_Name: SATURN-DIM-RING
Config: WFPC2
Opmode: IMAGE
Aperture: PC1-FIX
Sp_Element: FQCH4P15
Wavelength: 8922
Optional_Parameters: ATD-GAIN=15
CLOCKS=YES
Number_of_Iterations: 1
Time_Per_Exposure: 160S
Special_Requirements: MAX DUR 300S
POS TARG -2,-1
Data_Distribution
Medium: 8MM ! 8MM or 6250BPI or 1600BPI
Blocking_Factor: 10 ! 10 or 1
Ship_To: PI_Address ! STSCI or PI_Address or <free-text>
Ship_Via: UPS ! UPS (2-day) or OVERNIGHT