Double Star Status Report - April 2005
The European instruments are operating nominally. Resets on PEACE (electron sensor) are still occurring. The instrument is now switched on and off five times along the orbit to be able to recover from eventual resets.
Operations and Archiving
The European Payload Operation System (EPOS) co-ordinates the operations for the seven European instruments on TC-1 and TC-2 and is running smoothly. ESOC acquires data on average about 3.3 hours per day with the VILSPA 2 antenna. The availability of the antenna was above 99% between December 2004 and February 2005.
Previous Cluster observations have shown that the flapping motions of the Earth's magnetotail are of internal origin and that waves are emitted from the central part of the tail and propagate toward the tail flanks. Using conjunctions between Double Star and Cluster, simultaneous observations were made both at 10-13 and 16-19 RE. Neutral sheet oscillations were observed by the Cluster and Double Star satellites on 5 August 2004. The study showed that such waves can be observed as close to the Earth as 11 RE, in the neighbourhood of the magnetotail hinge point.
Very intense, solar activity occurred between 3 and 13 November 2004, stimulating one of the most intense episodes of geomagnetic storms. The Dst Index recorded at Kyoto University over the period concerned reached a maximum value of –383 nT. The NUADU instrument on Double Star TC-2 observed from over the North Pole Energetic Neutral Atoms (ENAs) produced in association with the great enhancement of the ring current produced during the storm. The emissions wrapped around the Earth from midnight to dusk. The ENA intensity was strong at midnight because of the high flux of parent ions. An ENA image was recorded simultaneously by the HENA experiment on the IMAGE spacecraft which was at that time located in the Southern hemisphere, and thus viewed the ring current from the South. The general morphology displayed in the two images is consistent. These are the first comparisons made between dedicated ENA images of the ring current taken simultaneously from two separated points in space.
A total of 27 Papers have been submitted for the special Annales Geophysicae issue on first results from Double Star. They are now in the review cycle. A special session on results from Double Star and Cluster will take place at the EGU in Vienna. This will be the first time that Double Star results are shown in an international conference.