Meet the RSSG (Continued)
In our May 1995 issue, you met the Remote Sensing Science Group (RSSG). Let's look a
bit closer at the activities of the teams that support the four remote-sensing science
instruments mounted on Galileo's scan platform: the solid-state imaging (SSI) subsystem,
the near-infrared mapping spectrometer (NIMS), the photopolarimeter/radiometer (PPR),
and the ultraviolet spectrometer (UVS), plus a fifth instrument, the extreme ultraviolet
(EUV) spectrometer mounted on the spinning part of the Orbiter.
Picture Taking--At a Distance
On October 11, the SSI camera will take a color image of the half-lit Jupiter. The SSI
Team Chief, Ken Klaasen, and Science Coordinators Herb Breneman,Todd Jones, Jim
Kaufman, Kari Magee, and Dave Senske are now focusing on the sequences for Orbits 7
and 8 of Jupiter. After a close-up view of Io at arrival, Orbits 1 and 2 will focus attention
on Ganymede, mixing global and high-resolution (1 km or better) images of selected
craters and other land features seen by Voyager. Global views will provide the context for
high-resolution shots, a combination that can lead us to an understanding of the history of
geologic events. Images in color will define boundaries between surface features whose
rocks and ice have differing chemical composition. The SSI will gather similar data on
Callisto on Orbit 3 and Europa during Orbits 4 and 6. Other sequences will include
monitoring volcanic activity on Io, noting changes from Voyager images; the study of the
Jovian inner small satellites and Jupiter's ring; and a close-up inspection of Jupiter itself.
While too near for global views, the team can "watch" from close range the plumes, hot
spots, and other atmospheric features previously spotted from Earth and Voyager. Their
data will also supplement the Probe's data on the Jovian atmosphere.
Besides planning sequences for each of the 10 orbits, the SSI team is busy assessing the
effect of the new data compression software that accommodates the low-gain antenna
requirements. To do this, they exercise the compression software, using Voyager and
Galileo cruise imaging data, and then compare it with precompression results. The team is
also studying the effects of radiation on their camera during passage through Earth's
radiation belt (Earth-2 approach 1992). Models developed will enable them to counter
image noise from Jupiter's strong radiation belt.
They Saw Venus From the Night Side
Infrared observations of the Jovian atmosphere and Galilean satellites are being
implemented by the NIMS Team Chief, Bill Smythe, and Science Coordinators Kevin
Baines, Elias Barbinis, Paul Herrera, John Hui, Rosaly Lopes-Gautier, Frank Leader,
Adriana Ocampo, and Marcia Segura. Their first-ever glimpse of the surface features of
Venus in the infrared occurred in 1990 during the Galileo Venus flyby, and their near-
infrared mapping spectrometer, NIMS, obtained exciting results from the Shoemaker-Levy
impact.
Now the NIMS team is eager for the December arrival of Galileo at Jupiter. At that time,
the Io flyby will offer them the opportunity to investigate the satellite's volcanic activity at
close range. From the many colors collected by NIMS, we can learn the average
composition of minerals and ices in small areas. For Io, NIMS will map the distribution of
sulfur dioxide and the temperatures of volcanos. The composition of the lineated areas on
Europa, the polar hood on Ganymede, and the large impact structures on Callisto will be
prime targets. Measurements of the satellite compositions and the temperature and
composition of swirling clouds and hot spots of Jupiter will continue throughout the tour.
Taking Their Temperature
Terry Martin, Science Coordinator for the Photopolarimeter/Radiometer (PPR) instrument,
and his assistants, Leslie Tamppari and Karen McBride, are planning the sequences needed
to collect thermal and reflected radiation data about satellite surfaces and atmospheric
properties. The PPR "takes the temperature" of clouds and gases in the upper Jovian
troposphere to develop a thermal radiation profile, using five spectral bands between 15
and 100 µm. The PPR data will tell us the temperature of the Galilean satellites and
the structure of Jupiter's atmosphere--the physical nature of the planet's clouds and gases
and how they are layered. We will learn about the texture and structure of the satellite
surfaces. Are they dusty or icy? Similar to a light meter (you may have a simple one on
your camera), the PPR measures the reflected sunlight in ten spectral channels between 410
and 945 nm.
The PPR instrument had its own chance to shine when it detected light flashes during the
fragment impacts of the S-L9 event. Its fixed stare at target Jupiter required no distracting
platform movement. Data were collected directly into the spacecraft computer and then sent
to the ground via the next memory readout (MRO). During that exciting week of comet
watching in July, 1994 data delivery was overnight. Other instruments were forced to tape
record their data and wait weeks or months for playback. The team reported its findings
immediately on a special World Wide Web exploder and in Science magazine this last July.
Viewing the Unseen Spectra
UVS/EUV Team Chief, Joe Ajello, and Science Coordinators John Aiello, Steve Edberg,
Keith Naviaux, and Kent Tobiska are planning their sequences to observe the UV spectra
of the Jovian planetary system and the magnetospheric plasma. Ninety percent of the data
will enter the real-time telemetry stream through the orbiter central computer (CDS) and be
downlinked at a rate of either one or two spectra per hour; the rest will be captured on tape.
Since the UVS can observe the entire ultraviolet-near-visible spectrum from 115 to 432 nm,
it will be able to detect emission, absorption, and scattering features in the unexplored 170-
to 432-nm wavelength region. The UVS team is also responsible for the EUV
spectrometer. This flight-spare Voyager UVS instrument was procured during the Galileo
redesign required by the Challenger loss. The EUV will be employed to follow up on
Voyager discoveries. It will observe sulphur and ion emissions from the Io torus and
atomic hydrogen auroral and airglow emissions from Jupiter. Joe has been busy analyzing
previous interplanetary Lyman 
and He (58.4 nm) emission
sprectra data; this cruise information is useful in predicting instrument performance on the
coming tour.
The Feature Track Campaign
Kent Tobiska, UVS Co-Investigator and Science Coordinator for ultraviolet atmospheric
auroral studies, described the campaign to efficiently collect data for a particular feature,
such as the Red Spot. Kent is a member of the Atmosphere Working Group (AWG) (one
of three such groups) formed to work in concert on a particular piece of science. The
AWG unites the instrument teams to integrate the capabilities of four of the remote-sensing
science instruments by instructing the NIMS, SSI, PPR, and UVS to collect data on the
same feature. The UVS, for example, will take data on a feature at many wavelengths
between 115 and 300 nm. These observations are simultaneous with the SSI images of the
same feature. This campaign technique proved its value during the recent comet
Shoemaker-Levy 9 impact event. Emissions observed by the UVS, combined with those
by the PPR and NIMS made it possible for the AWG to determine that the temperature of
the comet's G fragment fireball is a torrid 7500 K!
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