Hubble Servicing Mission SM4
Status Report #3
Great news to celebrate both for ESA and NASA yesterday! Two successful science mission launch events took place in one week: The amazing Atlantis launch for the servicing mission of the ESA/NASA Hubble Space Telescope and the impressive Ariane 5 launch of the ESA Herschel and Planck observatories.
Since the ESA HST team members have also been involved in the development of both satellites we happily joined, via the weblink, the ESA launch team celebrations in Kourou. This is a great day for science and the public. The 3.5 m telescope mirror of Herschel at the Lagrange point L2 will join the Hubble 3 m mirror at LEO and both telescopes with new cameras will allow unprecedented views of the evolution of galaxies and stars, the origin of the universe, black holes and dark matter.
EVA day 1
During yesterday's "orbit shift", the ESA HST team followed with great attention the critical events of the first EVA day. After depressurisation of the airlock, two astronauts moved head-first towards their work site. Tension rose when the astronauts experienced initial problems in the replacement of the Wide Field Camera 2. An attachment bolt for the camera didn't want to rotate under the applied release torque of the powered tool. Relief came when the astronaut used a manual torque wrench with applied higher torque. Great to have astronauts in these complex refurbishment tasks.
The new Wide Field Camera 3 was then successfully placed and also the next task of this EVA day, the replacement of the Science Command & Data Handling unit, was sucessfully achieved.
The planned replacement of some HST doors locks, aimed at easing the replacement tasks of hardware in the coming EVA days, posed some challenge. Fitting the new "EVA friendly" locks proved to be difficult in some locations.
Overall, a challenging EVA day of about 7 hours work; the key objective, the new camera placement and the science data handling unit repair have been well achieved. The two astronauts moved back through the airlock into Atlantis for a well deserved over-night rest. The functional testing during the "planning shift" of both replaced units proved successful and we are now up for a new challenging EVA day 2.
As anticipated by the ESA HST team, the replacement operations on the HST telescope caused the solar array wings to slip about 2 degrees from their original position, but this is not a point to worry about. By design, the applied SADM solenoid brakes provide limited holding capabilities, mainly aimed to hold the wings in position during the HST observing periods.
Prepared by Michael Eiden, 15 May 2009
Editor's note: The ESA HST team provides engineering support for the ESA hardware on the HST: the two Solar Array Drive Mechanisms (SADM), the Solar Array Drive Electronics (SADE), and the Drive Control Electronics (DCE).
The team comprises Michael Eiden (ESA HST Project Manager) and Lothar Gerlach from the technical directorate at ESA, and Udo Rapp and Manfred Schmid from EADS Astrium.