Un gigantesco flare (classe X-3) è stato espulso dal Sole il 13/12 in direzione della Terra, la tempesta ha creato alcuni problemi e le sonde che ne hanno subito le conseguenze sono, fra le altre: Integral, Cluster e Envisat. Per le tre sonde interplanetarie ESA è andata meglio perchè per un caso fortuito tutte e tre si trovano dal lato opposto del Sole (Mars Express, Venus Express, Rosetta
ESA mission controllers react to solar flare15 December 2006
An energetic storm on the Sun has forced ESA mission controllers to react to anomalies or take action to avoid damage to spacecraft. Several missions, including Integral, Cluster and Envisat, felt the storm’s effects, highlighting the need for ESA’s ongoing development of space weather forecasting tools.The joint ESA/NASA spacecraft SOHO (Solar & Heliospheric Observatory) imaged a large solar flare on 13 December that led to an energetic solar radiation storm.
The flare, detected by the LASCO (Large Angle and Spectrometric Coronagraph Experiment) spectrometer on board SOHO, gave rise to a powerful coronal mass ejection (CME), a stream of fast-moving atomic particles, directed towards Earth. The flare also generated X-rays.
The ejection arrived at Earth 14 December between 13:00-19:00 CET (12:00-18:00 UTC), where it gave rise to a strong geomagnetic storm; initial edges of the ejection were detected as early as 04:00 CET (03:00 UTC) on 13 December.
The coronal mass ejection came during a week of intense solar activity that is not yet over. An additional peak event occurred during the night of 14 December, and ground controllers on several ESA missions have reported varying effects on their spacecraft.
Four-spacecraft Cluster II mission was one of the most affected
“We saw three anomalies on 13 December. Cluster 1 had a minor instrument anomaly, while Cluster 2 and 4 had on-board systems affected,” says Juergen Volpp, Spacecraft Operations Manager for Cluster at ESA’s Space Operations Centre (ESOC) in Germany. “The Attitude and Orbit Control unit on Cluster 2 lost power and autonomously switched over to its redundant unit, while the High-Power Amplifier on Cluster 4 switched itself off. This was a new occurrence which we hadn’t seen before,” he said.
“When you have a burst, the flux of very fast charged particles increases dramatically. This can cause discharges in electronic components - the so-called ‘single-event upsets’ - on the spacecraft, as well as damage or loss of data in solid-state memories,” says Volpp.
Volpp says he can’t be certain that the increased energetic particle flux triggered the anomalies, but their occurrence is strongly correlated with the timing of the peak burst on 13 December. He expects the mission to be operating normally again in a few days.
Envisat & Integral affected
Envisat also experienced an unexpected anomaly correlated with the particle flux’s arrival at Earth.
“Operation of the Envisat Payload Module Computer was autonomously suspended, causing all payload instruments to be switched off. It happened around 19:00 CET, just before the particle peak on the 13th,” said Frank Diekmann, Spacecraft Operations Manager for Envisat. “We are still in a period of very high solar activity,” he added.
Controllers working on Integral had perhaps the best sense of the recent solar activity - two of the mission’s four instruments include the JEM-X and IBIS experiments, sensitive to X-rays and charged particles, respectively. However, they also had to take the most proactive action to avoid damage to the spacecraft’s sensitive sensors.
“JEM-X automatically switched itself into safe mode twice, and we manually switched IRIS off to avoid over-exposure,” says Michael Schmidt, Spacecraft Operations Manager for Integral.
ESA deep space missions avoid harm
The flurry of activity for controllers working on ESA missions orbiting in the region of the Earth was a direct result of Thursday’s coronal mass ejection heading more or less directly towards our planet.
“The mass ejection headed from the Sun to Earth and our planetary missions, on the other hand, weren’t affected,” explains Paolo Ferri, Head of the Solar and Planetary Missions Division at ESOC.
Ferri says that CME events are highly directional, and that by chance all three of ESA’s deep space missions, Mars Express, Venus Express and Rosetta, happen to be oriented on the side of the Sun opposite to the Earth right now. “Our interplanetary spacecraft didn’t see anything,” he adds.
However, radio signals transmitted from the three deep space missions must pass by the Sun to reach Earth, and so flight control teams could in fact notice the increased solar activity as higher-than-normal interference in the signals received on the ground.
, l’altro giorno avevano detto che per l’intera passeggiata erano stati guidati da Houston per evitare le radiazioni… ( penso abbiano un’idea un po’ contorta di tempesta solare…)