Hubble Servicing Mission 4 Blog

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 4 of the NASA/ESA 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 web link, the ESA launch team celebrations in Kourou, French Guiana.

Read more about Herschel and Planck. Read launch press release.

This is a great day for science and the public! The 3.5-metre telescope mirror of Herschel at the Lagrange point L2 will join the Hubble 3-metre mirror at low-Earth orbit 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.

During yesterday’s “orbit shift”, the ESA HST team followed with keen attention the critical events of the first EVA day. After depressurisation of the airlock, two astronauts moved head-forward towards their worksite. Tension rose when the astronauts experienced initial problems in the replacement of the Wide Field and Planetary Camera 2 (WFPC2). 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 (WFC3) was then successfully placed and also the next task of this EVA day, the replacement of the Science Command & Data Handling unit (Hubble’s main computer), was successfully 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 objectives, the new camera placement and the science data handling unit repair have been achieved. The two astronauts moved back through the airlock into Atlantis for a well-deserved overnight 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 it’s nothing to worry about. By design, the applied SADM (solar array drive mechanism) brakes provide limited holding capabilities, mainly aimed for holding the wings in position during the HST observing periods.