September-October 1982:JPL space report

IRAS

The first satellite survey of the celestial sphere in the infrared
portion of the spectrum will be accomplished by IRAS, a
cryogenic satellite scheduled for launch into a 900 km, Sun-synchronous orbit late this year. The project is an international endeavour, with JPL
managing the US half, The Netherlands managing the European half, and the UK supplying the tracking station and
associated support at the Rutherford and Appleton Laboratories near Chilton, England.

Data taken by the 60 cm telescope (sensitive in the 8 to 120
micron range) will be stored on a tape recorder and dumped
twice per day during passes over the Chilton station. These
data are electronically transferred to JPL and processed by the
Scientific Data Analysis System (SDAS), which is based upon
a highly sophisticated set of computer programmes designed
specifically for IRAS data processing.

The basic processing will be accomplished on an IBM 3032
and the primary product will be a catalogue of infrared point
sources, primarily stars and galaxies. Somewhere between
250,000 to 1,000,000 such sources are expected. This catalogue
should serve generations of astronomers as a guide to the
infrared sky and as a research tool to assist in identifying
interesting objects suitable for more detailed study.

Although the telescope does not directly produce photographic products, SDAS processing will yield photographic¬
like representations of large regions of the sky in order to show
bulk distribution of stars, dust, and gas.
After an initial “shakedown” period of two to three months
following launch, SDAS will process data within a few days of
receipt at the ground station. This prompt analysis will assist
mission planners in their assessment of mission progress, and
may result in changes to the strategy of sky coverage.

The JPL project manager for IRAS is Gerald M. Smith. John
H. Duxbury manages SDAS, and Dr. B. T. Soifer of Caltech
is the principal science advisor for SDAS matters.

LOW-COST PLANETARY MISSIONS

The Mariner Mark II project (MMII) was initiated recently
at JPL in order to develop a set of planetary missions which
will allow continued exploration of the Soiar System under
very tight budget constraints.
The central idea is to design the mission “set" so that a
relatively constant yearly expenditure suffices. The fiscal target
is a cost of about $100 million (1982 dollars) per year for the
funding of four to five missions launched in the 1989 to 1998
period. Focussed science, reduced complexity, and maximised
inheritance (hence the Mariner Mark II designation) are key
to achieving the MMII goals.

The mission set for MMII is still under study but several
mission types are being considered:

1. Comet rendezvous

2. Comet intercept/sample return

3. Asteroid rendezvous (near Earth and main belt)

4. Mars orbiter

5. Titan flyby/Titan probe

6. Saturn orbiter/Titan mapper

The indicated launch vehicle for these missions is the
STS/IUS 2-stage with or without the STAR-48 kick stage.

SHUTTLE EXPERIMENTS

Two of the seven experiments aboard the Space Shuttle
Columbia were designed by JPL for the scientific payload flown
12-14 November 1981.

The Shuttle Imaging Radar-A (SIR A) represents a natural
outgrowth from a JPL technological base for synthetic aperture
radars (SAR), one of which was employed on the 1978 Seasat
oceanographic satellite. The SAR technology also played a
prominent role in the design of the Venus Orbiting Imaging
Radar mission (VOIR), now cancelled due to budgetary
constraints.

SIR-A obtained eight hours of data covering ten million
square kilometers of Earth, including a 45 minute swath from
Spain, through the Mediterranean, and out to India and
Australia.

The primary advantage of SAR observations over more
conventional optical images is that the SAR supplies its own
microwave illumination and is not limited by the presence of
clouds or the lack of sunlight. After processing, the SIR-A
system can yield a spatial resolution of 40 m. This resolution
is obtained using an antenna which measures 9.35 by 2.0 m.

The failure of a fuel cell onboard Columbia necessitated an
early return to Earth and a resultant disruption of the original
mission design for the SIR-A experiment. However, using a
microcomputer equipped with an advanced graphical software
package. Henry Harris (team leader) and Joan Pojman of JPL
rapidly redesigned the experimental procedures, and a new set
of commands was sent to the crew in time to successfully
obtain the data.

The Principal Investigator for the SIR A experiment was Charles Elachi of JPL.

The second experiment, the Shuttle Multispectral Infrared
Radiometer (SMIRR), was flown in order to investigate Earth
resources.

The spectral reflectance of rocks and soil on the surface of
the Earth permits inferences to be made concerning the composition of surface materials or possible petroleum deposits
below the surface. The system consists of a 17.8 cm telescope
(derived from a telescope flown on the 1973 Mariner 10 Mission
to Venus and Mercury), filters, detectors, and other supporting
equipment. Ten bands within the 1.0 to 2.5 micron portion of
the infrared were tested for effectiveness in providing clues to
surface composition. Since the SMIRR is not an imaging
device, two cameras (one colour and one black and white) were
aligned with the SMIRR telescope to provide images which
can be correlated with the SMIRR data.

Initial results obtained from analysis of the data from this
instrument were announced at a meeting of the American
Society of Photogrammetry in Denver. Colorado in March
1982. In one case the SMIRR appears to have surpassed normal
field techniques in the ability to differentiate between minerals!

The Principal Investigator was Dr. Alexander Goetz of JPL.