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W4DPH > SAT 23.03.03 03:35l 60 Lines 2768 Bytes #999 (0) @ AMSAT
BID : ANS-082.08
Read: DB0FHN GUEST
Subj: Artemis Relays First Envisat Images
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Sent: 030323/0136Z @:W4DPH.#TPA.FL.USA.NOAM #:51528 [CLW] FBB $:ANS-082.08
From: W4DPH@W4DPH.#TPA.FL.USA.NOAM
To : SAT@AMSAT
AMSAT News Service Bulletin 082.08 From AMSAT HQ
SILVER SPRING, MD. March 23, 2003
To All RADIO AMATEURS
BID: $ANS-082.08
The first satellite-relayed images from Envisat have been received, via the
Artemis data-relay spacecraft in geostationary orbit, at the European Space
Agency's data processing centre near Rome.
For Artemis, the Advanced Relay Technology Mission, the image transmission
caps a historic, 18-month recovery operation that brought the spacecraft to
its assigned geostationary orbit at 21.5 degrees East after a July 2001
launch that left Artemis stranded in an orbit far lower than intended.
Artemis carries payloads supporting land mobile communications, navigation
systems and data relay systems. The spacecraft operates at S-band (2 GHz),
Ka-band (26 GHz) and optical frequencies. Artemis and Envisat communicate at
Ka-band frequencies.
Setting up the operational data relay system in the Ka-band between Artemis
and Envisat is a first for Europe. The system proves the space
qualifications of new technologies and operational procedures, along with
demonstrating the complex software used in both the ground and space
segments. It also shows the usefulness of data relay payloads.
Data from various instruments will continue to be downloaded to the Envisat
ground station and data processing centre in Sweden, but the addition of the
data relay satellite offers several important new capabilities to the
Envisat data network.
The Swedish ground station can 'see' the satellite for about 10 minutes of
Envisat's 100-minute orbit, and for 10 daily orbits. Because of its orbital
position above Envisat, Artemis can remain in contact with Envisat on almost
all its 14 daily orbits, and for longer periods.
The use of Artemis will also enable the European Space Agency to increase
the amount of data acquired by Envisat anywhere in the world, particularly
in the case of the Advanced Synthetic Aperture Radar
(ASAR) instrument, increase the flexibility of the mission's ground segment,
and provide a back-up in the event of a problem with the onboard recorders,
which will improve mission reliability.
Envisat recently marked its first year in orbit. Launched on 28 February
2002 from Europe's spaceport in French Guiana, it is the largest and most
capable Earth observation satellite ever built. Its suite of 10 sensors is
designed to provide a comprehensive view of the Earth's oceans, land,
atmosphere and ice caps.
The optical data relay system will be used between Artemis and the French
Earth observation satellite, SPOT 4, starting in April. In 2005 the
Automatic Transfer Vehicle will start using a regular data relay
[ANS thanks Space Daily for the above information.]
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