French Advances in Science and Technology #300 (Excerpts)

** JASON IN THE SKY WITH TOPEX

After nearly nine years of faithful service, the satellite that accomplished
such firsts as tracking the development of El Nino live by observing local
changes in ocean levels is going to get some relief. The Franco-American
Topex-Poseidon satellite was joined in orbit last week by Jason, another
Franco-American offspring, after successful launch from Vandenberg Air Base
in California. The other thing that went up from Vandenberg was a collective
sigh of relief after a series of minor but nagging setbacks had slowed the
program’s calendar. (One French scientist joked that JASON stands for
“problems in July August, September, October November.)

Project officials
reported clear and complete data reception as Jason hit its orbital path.
The diminutive Jason, built by Alcatel Space and a featherweight satellite
at a half-ton or five times lighter than Topex-Poseidon, is capable of even
bigger feats than its predecessor, measuring ocean surface topography with a
precision down to a millimeter of altitude (compared to less than a
centimeter for T-P). Not only is the altimeter on board Jason, Poseidon-2,
an improvement, but a more complex infrastructure has been put in place to
locate Jason more exactly, thus permitting more exact calculations of the
distance traveled by the signals bounced off the ocean surface by its
radar/altimeter. The location system is a three-part harmony of a GPS
marker, a reflector on board Jason sending laser signals back to tracking
stations, and Doris. The latter is a system devised by the French National
Space Studies Center (CNES) in conjunction with several French laboratories.
Jason is equipped with a Doris antenna by which 50 dry land tracking beacons
around the world are in constant touch with the satellite. Correcting these
already precise readings to render them more accurate still is the job of a
NASA-designed radiometer capable of measuring the slowdown in the
altimeter-emitted radar waves due to atmospheric interference.

Plans call
for Jason to follow right behind T-P in the same orbit to enable project
scientists to calibrate Jason’s readings to match what they’ve been
receiving from T-P, thus ensuring continuity of data. Afterwards Jason will
take up a position alongside its forebear, and oceanographic researchers,
like project scientists from IFREMER, will have what they dream of: twice as
much data. In any case, continuity is the keyword, as the light, cheap Jason
is a machine that can regularly be replaced so that a wide variety of
research specialties and applications will be able to benefit from a regular
stream of the type of readings that have revolutionized understanding of
oceans and climates since 1992. IFREMER’s director of oceanographic research
predicts that altimetric ocean readings will become as indispensable as
satellite meteorological images are today. (Le Monde, Pierre BarthŽlŽmy,
December 12, p26)

VLT/CHILE.

FAST #255 reported on the European Southern Observatory’s project
to install a system called NAOS (Nasmyth Adaptive Optic System) on at least
one of their very large telescopes on Mount Paranal to correct for
atmospheric distortion. NAOS, which is based on a continuously deformable
mirror reacting to readings on actual distortion, and which has been
designed and built by the Paris Observatory, the Grenoble Observatory, the
CNRS’s National Institute for Space Science, and Onera (a publicly-held
French aerospace contractor), has just been installed and tested. The first
corrected light signals were infrared images supplied to CONICA, an infrared
camera developed by the Max Planck Institute, and they do in fact permit
CONICA to see a great deal more clearly. The camera has recorded objects
both within and beyond our galaxy which were previously unavailable. (CNRS
CommuniquŽ, December 4)

ASTRONOMY EUROPE.

The European Commission has voted nearly $4 million for the
development of the Astrophysics Virtual Observatory (AVO), a project to
assemble online the billions of images recorded by telescopes around the
world and currently stored in archives. As waiting lines lengthen for
viewing time at major installations, the AVO would provide ready access to a
pre-recorded virtual heaven. The European project is expected to take three
years to develop, at which point it will likely be synched-up with a similar
American project (NVO). (LibŽration, December 6, p27)