Proposal 11562 (STScI Edit Number: 0, Created: Monday, July 7, 2008 8:41:50 PM EST) - Overview
11562 - Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus
Cycle: 17, Proposal Category: GO
(Availability Mode: SUPPORTED)
INVESTIGATORS
Name
Dr. Heidi B. Hammel (PI)
Dr. Kathy Rages (CoI)
Prof. Imke de Pater (CoI)
Dr. G. Wes Lockwood (CoI)
Institution
Space Science Institute
SETI Institute
University of California - Berkeley
Lowell Observatory
E-Mail
hbh@alum.mit.edu
krages@mail.arc.nasa.gov
imke@astron.berkeley.edu
gwl@lowell.edu
VISITS
Visit Targets used in Visit
Configurations used in Visit
Orbits Used Last Orbit Planner Run
01
(1) URANUS
WFC3/UVIS
1
07-Jul-2008 21:41:35.0
OP Current
with Visit?
yes
02
(1) URANUS
WFC3/UVIS
1
07-Jul-2008 21:41:41.0
yes
03
(1) URANUS
WFC3/UVIS
1
07-Jul-2008 21:41:46.0
yes
3 Total Orbits Used
ABSTRACT
The planet Uranus is demonstrating increased atmospheric activity as it passes the equinox, likely in response to extreme insolation change.
Convective sites in the planet's southern hemisphere reached unprecedented altitudes in 2003 (Hammel et al. 2005, Icarus 175, 284); a bright
northern feature showed the highest contrast yet detected in an outer planet atmosphere (Sromovsky et al. 2007, Icarus 192, 558); and a dark
atmospheric feature was detected by HST in late 2006 (Hammel et al. 2008, in preparation). The historical record makes references to discrete
Proposal 11562 (STScI Edit Number: 0, Created: Monday, July 7, 2008 8:41:50 PM EST) - Overview
structures (both bright and dark) on Uranus during previous equinoctial apparitions (the last equinox occurred in 1965). The best amateur facilities
are now just able to resolve the disk of Uranus and detect such activity if it is very large or has very high contrast. Amateurs also have access to a
great many nights of telescope time. If a discrete cloud feature on Uranus is reported through the amateur network, we propose to obtain follow-up
images with HST's WFC3. The proposed TOO images will permit determination of detailed structure of the feature at visible wavelengths, and will
provide vertical and horizontal constraints on the feature's scattering properties. HST is the only facility that can provide such information at visible
wavelengths. The proposal was accepted in C16, but not executed because the defined criteria for activation were not met. Because the timescales of
change on Uranus are unknown, we resubmit this for Cycle 17.
OBSERVING DESCRIPTION
Proposed Observations: We received three orbits of WFC3 imaging in Cycle 17 to make Target of Opportunity observations of an anomalous feature
on Uranus with WFC3.The first orbit should be as soon as possible after discovery, preferably within a few days but this is not critical. We estimate
a TOO feature would have a lifetime of perhaps many months. Each orbit should have the feature as close as possible to the central meridian to
permit optimal imaging of detailed structure. The TOO trigger conditions require that the feature’s rotation period be known prior to TOO execution;
thus the location of the feature relative to the central meridian will be known as well. The feature will likely have a rotation period of order 16-17.5
hours, based on past HST and Keck imaging. The second orbit should occur about 35 hours (two rotations of Uranus, or 22 HST orbits) after the first
orbit. The third should follow about 35 hours after that. The function of the two additional orbits is to characterize the horizontal and vertical
evolution of the feature in much the same manner as was done with HST for Saturn’s Great White Spot and Uranus’ dark spot and its companions.
Filter Specifics: The methane sets probe the vertical aerosol distribution of cloud features as a function of altitude. Also, our filter choices provide
continuity both with those used for past HST observations and with past ground-based observations. The exposures are based on prior HST images
made with similar filters or ETC calculations using ground-based spectroscopy as input. The times are optimized for the “typical” Uranus, and are
appropriate for an anomalously dark feature. If an anomalously bright feature is seen, then the times will be reduced further, and perhaps one
additional filter might be included.
WFC3 — Exp (s) — SNR — Comment
2
Proposal 11562 (STScI Edit Number: 0, Created: Monday, July 7, 2008 8:41:50 PM EST) - Overview
F467M — 16 — 200 — Strömgren b; Lockwood filter; max Neptune GDS contrast
F547M — 6 — 200 — Strömgren y; Lockwood filter; showed Uranus GDS
FQ619N — 100 — 100 — 619-nm weak CH4 band; expected condensation CH4 level
F631N — 22
100 — Continuum as well as contrast for features *
F658N — 100 — 100 — Continuum; Max contrast for Uranus GDS in C15
FQ727N — 160 — 70 — 727-nm medium methane band
FQ750N — 60 — 114 — Continuum near 727-nm CH4 band
F775W — 20 — 40 — Near-IR cont. with some CH4 absorption
F845M — 35 — 153 — Near-IR cont. with some CH4 absorption; feature contrast
F889N — 360 — 45 — CH4 absorption of 25 km–1atm–1
F906N — 300 — 67 — CH4 absorption of 2.5 km–1atm–1
F924N — 200 — 99 — CH4 absorption of 0.25 km–1atm–1
F937N — 160 — 103 — CH4 absorption of 0.025 km–1atm–1
* Added since Phase 1 at the request of co-I. Does not duplicate any other Uranus observations (past or future) since the images being scheduled
here are target-of-opportunity observation of a specific atmospheric feature.
Filters in each orbit: In orbits 1 and 3, we use most of a filter set designed for outer planet observations near the methane absorption band near 889
nm as well as a matched methane-continuum pair near 727 nm; filters corresponding to Strömgren b and y filters used for long-term brightness
monitoring; and the F658N filter similar to one that showed maximum contrast for the Uranus dark spot in C15. In orbit 2, we sample some of the
same 889-nm methane filters; a matched methane-continuum pair near 619 nm; and filters with good contrast for discrete features. We will not
dither due to short exposure times (dithering imposes a 2.5-min penalty for splitting the exposure, and dithering several exposures could require a
5.6-min buffer readout). We will use sub-arrays to avoid the need for buffer readouts during our planned visits. Comparisons with images at nearby
wavelengths will permit identification of artifacts and cosmic rays.
Orbit Filters
3
Proposal 11562 (STScI Edit Number: 0, Created: Monday, July 7, 2008 8:41:50 PM EST) - Overview
1 F467M, F547M, F631N, F658N, FQ727N, FQ750N, F889N, F924N, F937N
2 F467M, F547M, F631N, F658N, F775W, F845M, FQ619N, FQ889N, FQ906N, FQ937N
3 F467M, F547M, F631N, F658N, FQ727N, FQ750N, F889N, F924N, F937N
ADDITIONAL COMMENTS
Target of Opportunity Proposal
4
Solar System Targets
Visit
Proposal 11562 - Visit 01 - Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus
Proposal 11562, Visit 01, implementation
Diagnostic Status: No Diagnostics
Scientific Instruments: WFC3/UVIS
Special Requirements: ON HOLD
On Hold Comments: Target of opportunity
#
Name
Level 1
(1)
URANUS
STD=URANUS
Exposures
#
1
Label
Tue Jul 08 01:41:50 GMT 2008
Level 2
Level 3
Target
(1) URANUS
Config,Mode,Aperture
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
Spectral Els.
F467M
Opt. Params.
CR-SPLIT=NO
2
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F547M
CR-SPLIT=NO
3
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F631N
CR-SPLIT=NO
4
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F658N
CR-SPLIT=NO
5
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ727N
CR-SPLIT=NO
6
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ750N
CR-SPLIT=NO
7
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ889N
CR-SPLIT=NO
8
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ924N
CR-SPLIT=NO
9
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ937N
CR-SPLIT=NO
5
Window
Special Reqs.
Groups
Ephem Center
EARTH
Exp. Time/[Actual Dur.]
18 Secs
[==>]
6 Secs
[==>]
22 Secs
[==>]
140 Secs
[==>]
200 Secs
[==>]
60 Secs
[==>]
360 Secs
[==>]
200 Secs
[==>]
160 Secs
[==>]
Orbit
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
Orbit Structure
Proposal 11562 - Visit 01 - Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus
6
Solar System Targets
Visit
Proposal 11562 - Visit 02 - Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus
Proposal 11562, Visit 02, implementation
Diagnostic Status: No Diagnostics
Scientific Instruments: WFC3/UVIS
Special Requirements: AFTER 01 BY 34 H TO 36 H; ON HOLD
On Hold Comments: Target of opportunity
#
Name
Level 1
(1)
URANUS
STD=URANUS
Exposures
#
1
Label
Tue Jul 08 01:41:51 GMT 2008
Level 2
Level 3
Target
(1) URANUS
Config,Mode,Aperture
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
Spectral Els.
F467M
Opt. Params.
CR-SPLIT=NO
2
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F547M
CR-SPLIT=NO
3
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F631N
CR-SPLIT=NO
4
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F658N
CR-SPLIT=NO
5
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F775W
CR-SPLIT=NO
6
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F845M
CR-SPLIT=NO
7
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ619N
CR-SPLIT=NO
8
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ889N
CR-SPLIT=NO
9
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ906N
CR-SPLIT=NO
10
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ937N
CR-SPLIT=NO
7
Window
Special Reqs.
Groups
Ephem Center
EARTH
Exp. Time/[Actual Dur.]
18 Secs
[==>]
6 Secs
[==>]
22 Secs
[==>]
140 Secs
[==>]
20 Secs
[==>]
60 Secs
[==>]
100 Secs
[==>]
360 Secs
[==>]
300 Secs
[==>]
160 Secs
[==>]
Orbit
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
Orbit Structure
Proposal 11562 - Visit 02 - Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus
8
Solar System Targets
Visit
Proposal 11562 - Visit 03 - Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus
Proposal 11562, Visit 03, implementation
Diagnostic Status: No Diagnostics
Scientific Instruments: WFC3/UVIS
Special Requirements: AFTER 02 BY 34 H TO 36 H; ON HOLD
On Hold Comments: Target of opportunity
#
Name
Level 1
(1)
URANUS
STD=URANUS
Exposures
#
1
Label
Tue Jul 08 01:41:52 GMT 2008
Level 2
Level 3
Target
(1) URANUS
Config,Mode,Aperture
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
Spectral Els.
F467M
Opt. Params.
CR-SPLIT=NO
2
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F547M
CR-SPLIT=NO
3
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS1-M512-SUB
F658N
CR-SPLIT=NO
4
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ727N
CR-SPLIT=NO
5
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ750N
CR-SPLIT=NO
6
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ889N
CR-SPLIT=NO
7
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ924N
CR-SPLIT=NO
8
(1) URANUS
WFC3/UVIS, ACCUM,
UVIS-QUAD-SUB
FQ937N
CR-SPLIT=NO
9
Window
Special Reqs.
Groups
Ephem Center
EARTH
Exp. Time/[Actual Dur.]
18 Secs
[==>]
6 Secs
[==>]
140 Secs
[==>]
200 Secs
[==>]
60 Secs
[==>]
360 Secs
[==>]
200 Secs
[==>]
160 Secs
[==>]
Orbit
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
Orbit Structure
Proposal 11562 - Visit 03 - Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus
10