zmapj36@sund.cc.ic.ac.uk (M.S.Bennett Supvs= Prof Pendry) (06/26/90)
IN BRIEF-(taken from the ESA bulletin No.62 May 1990)
ESA/USSR Cooperative Agreement
==============================
An agreement on cooperation in the exploration and use of sapce for
peaceful purposes between the Goverment of the Soviet Union and ESA was signed
on 25 April at ESA Headquarters in Paris, by the Soviet Union's Ambassador, His
Excellency Iakov Riabov, and the Agency's Director General, Prof. Reimar Lust.
The Agreement is for an initial period of ten years and covers a wide
range of space activities, including: exploration of the Solar System, space
astronomy and astrophysics, Earth observation and meteorology and life
sciences. Working groups will be esablished for each of these disciplines, to
investigate and recommend potential cooperative projects.
ESA has a long history of scientific cooperation with the Soviet Union,
the formal basis of which has until now been an Exchange of Letters between the
Soviet Academy of Sciences and ESRO (one of ESA's forerunners), largely
concerned with the exchange of scientific information. One of the most
spectacular of past cooperative ventures was the encounter with Halley's Comet
in 1986 by ESA's Giotto, two Soviet spacecraft, Vega-1 and -2, as well as two
Japanese spacecraft. Amongst other joint projects, ESA experiments were flown
aboard the Soviet space biology missions, Biokosmos-8 and -9 in 1987 and 1989.
In February this year an International Workshop was held in Graz, Austria,
to discuss the scientific aspects of cooperation between ESA's Cluster project
and the Soviet Regatta mission.
******
Hipparcos Survives Solar Eclipse
================================
Soon after Hipparcos became trapped in its highly elliptical orbit, the
operations team realised that a critical test of the satellite's power system
would occur around mid-March, when the satellite would have to endure extended
periods of solar eclipse.
For three weeks the solar arrays were in shadow for a much longer period
each day than the 72 minutes foreseen in the nominal circular orbit. During
these eclipses, the spacecraft had to rely soley on battery power.
Prior to the maximum eclipse period, about 105 minutes on 16 March,
contingency plans were put into action at ESOC to shut down elements of the
payload to limit the drain on the batteries. The satellite survived this
critical event with a power margin of barely five minutes and scientific
measurments were able to proceed without interruption.
The fourth ground station, the NASA Goldstone station in Mohave desert in
California, is now on line, increasing the amont of scientific data that can be
retrieved from the satellite.
******
Giotto Reactivated
==================
On 19 Febuary 1990 a faintly whispered radio signal was received at the
Madrid tracking station of NASA's Deep Space Network. The signal was from
Giotto, the ESA probe that has been hibernating in deep space since its
spectacular encounter with Halley's comet in March 1986.
Preperations have been underway since May 1988 at the Agency's Operations
Center (ESOC) in Darmstadt, Germany, to reactivate the spacecraft. Beginning on
19 February, a series of telecommands was transmitted to Giotto via the Madrid
tracking station, using a 70m antenna and a 100000 W transmitter, many thousand
times the power of a TV broadcasting station. The first faint reply was
received when Giotto was about a hundred million km from Earth
The mission control team at ESOC then performed a series of complex
manoeuvers to point Giotto's high-gain antenna towards the Earth in order to
increase the strength of the signals, so that a complete check-out of the
spacecraft could be performed.
The first of a series of manoeuvres to target Giotto for its new mission,
an encounter with comet Grigg-Skjellerup, was performed in mid-March. Giotto
was then 75 million km from Earth. The temperature of the spacecraft was found
to be too high, because of damage to the thermal insulation and thermal
surfaces during the Halley encounter. However, as Giotto moves further from the
Sun, the spacecraft should cool down, and checking-out of the scientific
instruments can begin, from end-April onwards. (NOW) In the meantime periodic
orbit control manoeuvres are being performed.
On 2 July 1990 Giotto will pass within 23000 km of Earth, and the Earth's
gravitational field will be used as a 'slingshot' force to propel the
spacecraft on towards its new target.
******
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| ====================== |dieter@rwthinf.UUCP (Dieter Kreuer) (06/26/90)
In article <1990Jun25.175946.20917@cc.ic.ac.uk>, zmapj36@sund.cc.ic.ac.uk (M.S.Bennett Supvs= Prof Pendry) writes: > ****** > > Giotto Reactivated > ================== > > > On 2 July 1990 Giotto will pass within 23000 km of Earth, and the Earth's > gravitational field will be used as a 'slingshot' force to propel the > spacecraft on towards its new target. > A friend of mine uses to watch geostationary satellites with a C8 and has written a program for determining equatorial coordinates when geocentric elements for the satellite are provided. He uses stars as a guide to direct the scope to the desired position and switches off the drive when the satellite crosses the field of view. Is the Giotto probe also visible with an 8 inch as it passes Earth, though it has no large solar panels? How fast will it move (angular velocity)? Can anybody provide geocentric elements or even a table of guide stars for 50.8 deg N, 6.5 deg E (if the event does not take place by daylight)? URGENTLY, this net can be quite slow sometimes! ------------------------------------------------------------------------------ Dieter Kreuer, Lehrstuhl Informatik IV, RWTH Aachen, Ahornstr. 55, D-5100 Aachen; dieter@informatik.rwth-aachen.de; dieter@rwthinf.uucp ------------------------------------------------------------------------------
dmc@videovax.tv.tek.com (Donald M. Craig) (06/26/90)
In <1990Jun25.175946.20917@cc.ic.ac.uk> seds@cc.ic.ac.uk (M.sean Bennett) writes: "Beginning on 19 February, a series of telecommands was transmitted to Giotto via the Madrid tracking station, using a 70m antenna and a 100000 W transmitter, many thousand times the power of a TV broadcasting station." Reaching for my trusty Television and Cable Factbook, which lists in gory detail facts about all US television stations, I extracted the following: KNLC, Channel 24 (530 - 536 MHz), St. Louis, MO, Authorized power: 3090-kw max. visual, 309-kw max.aural. WTZA, Channel 62 (758 - 764 Mhz), Poughkeepsie, NY, Authorized power: 5000-kw max. visual, 500-kw max. aural. KICU, Channel 36 (602 - 608 MHz), San Jose, CA, Authorized power: 4098-kw max. visual, 410-kw max. aural. That's 3 million watts, 5 million watts, and 4 million watts. Perhaps the 100000 W number was a typo? cheers, Don Craig Tektronix Television Division, dmc@tv.tv.tek.com