Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

GIOVE-B spacecraft in good health

30.04.2008
After its successful launch by a Soyuz Rocket from Baiknour on 27 April and accurate insertion into its target orbit by the Fregat autonomous upper stage, GIOVE-B is now completing its Launch and Early Operations Phase (LEOP), which will shortly give way to the platform commissioning phase.

Platform commissioning includes the on-board verification of all primary and redundant platform subsystems, namely telemetry and telecommand, propulsion, power, thermal control, and attitude and orbit control. GIOVE-B operations are being carried out from Telespazio's Fucino Space Centre in Italy.

Once the spacecraft platform has been commissioned, switch-on of the various payload elements can begin. First signal transmission is anticipated in the coming days.

Charging the batteries

Since the spacecraft had been running on battery power from just before liftoff - throughout the lengthy series of manoeuvres performed by Fregat to reach the intended orbit - the first tasks after separation from Fregat were to deploy the solar arrays and achieve Sun-pointing, so that battery charging could begin.

The first-choice method to turn the spacecraft for Sun-pointing is to use the reaction wheels. GIOVE-B is equipped with four gyroscope-like wheels driven by brushless electric motors. Altering the speed of rotation of these wheels allows the satellite to be rotated in space.

Use of the reaction wheels for initial pointing is the first choice because, once they are operational, the supply of electricity from the solar arrays is essentially unlimited. However, due to the battery discharge that occurred during pre-orbital flight, the spacecraft operations manual only allows a restricted time for these manoeuvres to be accomplished.

Attitude and orbit control

GIOVE-B's reaction wheels were slow to respond and stable Sun-pointing was not achieved within the specified time period. As a consequence, around five hours after launch it was decided to put the satellite into safe mode, and Sun-pointing was achieved using small engines known as thrusters.

The initial underperformance of the reaction wheels was found to have occurred due to a mismatch between the on-board avionics software and the reaction wheel calibration data. This has now been corrected by the uploading of a software patch to the spacecraft, leading to nominal performance.

Use of the thrusters is the second-choice method because one of the factors determining the operational life of GIOVE-B is the amount of propellant that the spacecraft carries. The thrusters are used for orbital station-keeping and conservation of propellant is important to maximise the lifetime of the spacecraft. Once the propellant is nearly exhausted, the thrusters' final task is to lift the spacecraft into a 'graveyard' orbit at the end of its mission - to free the orbit for the operational Galileo constellation.

Payload switch-on

Once the GIOVE-B spacecraft platform is fully commissioned, the navigation payload can be switched on. The rubidium and passive hydrogen maser clocks will be started first, followed by the navigation signal generator.

The final units to be turned on will be the transmit chain consisting of L-band solid-state power amplifiers that broadcast the Galileo signals to the Earth. First signal transmission is anticipated in the coming days and will be received and calibrated by In-Orbit Test (IOT) facilities deployed at ESA's ground station in Redu (Belgium) and at Chilbolton Observatory in the UK.

Dominique Detain | alfa
Further information:
http://www.esa.int/SPECIALS/GIOVE-B_launch/SEMZWWTQMFF_0.html

More articles from Physics and Astronomy:

nachricht New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center

nachricht Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>