Each year, in autumn, the Cluster fleet must pass several times through the Earth's shadow with respect to the Sun. During these eclipses, which last about three hours, sunlight is blocked by the Earth and the spacecraft solar panels cannot generate electricity.
Batteries then generate electrical power, which is used to run heaters - keeping the spacecraft warm - and to operate on-board computers and maintain spacecraft control.
However, the Cluster fleet, launched in mid-2000, has been in orbit for over six years and batteries, in particular, are beginning to age. This year, spacecraft No. 1, Rumba, had the most severe battery problems; three out of five have already been declared non-operational for nominal use and one has a high leakage current.As a result, mission engineers forecast that only about half of the battery power required by Rumba would be available during eclipse season.
The team created a computer model of the spacecraft's thermal behaviour to identify how, exactly, it could survive eclipses with reduced, or even with no, active heaters. There were also issues with the on-board computer, designed to restart itself automatically in the event that power is ever lost.
"The most difficult aspect was to find a safe method to switch off the onboard computer, deactivating its auto-recovery function and then to be able to wake it up again from its 'artificial coma' after the eclipse," said Juergen Volpp, Spacecraft Operations Manager at ESOC, in Darmstadt, Germany.
When the predicted eclipse passage ended at 22:13 UTC (00:13 CEST), engineers sent commands to wake the on-board computer. They had to wait one minute for the computer to restart itself, plus four seconds of telemetry processing and signal travel time. "We never thought that sixty-four seconds could seem so long," said Volpp.
But the meticulous preparations and months of planning paid off handsomely as Rumba emerged from the shadow, grabbed the wake-up signal and powered up its computer just as expected; controllers quickly verified that nothing onboard had cooled below acceptance temperatures, and all systems were back in operation a few hours later.
The strategy was again proven two days later during the next - and longest - eclipse, early on 18 September. The last eclipse was successfully negotiated on 20 September and the Cluster fleet is now back in nominal operation, continuing one of ESA's most successful astrophysics missions.
Juergen Volpp | EurekAlert!
First Juno science results supported by University of Leicester's Jupiter 'forecast'
26.05.2017 | University of Leicester
Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy