Hubble Servicing Mission 4 Blog

Astronaut John Grunsfeld completes the final tasks of Servicing Mission 4. Image credit: NASA

“Today begins the second Hubble revolution.” - David Leckrone, Senior Project Scientist for Hubble Space Telescope

Status Report 5 of the ESA HST support team at NASA GSFC: issued Tuesday 19.5.2009 shortly after successful in-orbit release of the HST from the Atlantis orbiter

HST SM 4: Servicing Mission accomplished - full mission success

After successful completion by the astronauts of five days of EVA (spacewalk) refurbishment/repair activities for HST, the telescope has just been released into orbit by the grapple fixture of the Atlantis Remote Manipulator System (robotic arm).

The planned replacement of COSTAR and WFPC2 with the Cosmic Origins Spectrograph (COS) and the Wide Field Camera (WFC3) has been accomplished and functional testing was successful.

The unprecedented in-orbit repair of Hubble’s scientific instruments (not designed for in-orbit maintenance) proved to be extremely challenging, however, was successfully completed.  It was the versatility of humans in space and the use of many new tools specifically developed for these repair tasks that allowed for such resounding success. However, space hardware always bears the potential for surprises. In one case, a bolt removal on a handrail on STIS showed no success, even using all tools available to the astronaut. Supported by real time on-ground validation of required forces, the astronaut had to apply “brut force” to remove the handrail by breaking off the bolt. Otherwise, the handrail would have obstructed the necessary placement of the STIS repair tool.

Functional testing has confirmed the successful repair of the Advanced Camera for Surveys (ACS), though with the exception of its high-resolution channel, and of the Space Telescope Imaging Spectrograph (STIS).

The successful replacement and in-orbit functional validation testing of the following HST subsystems/units provides operational capabilities for many years, potentially extending the HST in-orbit life towards 2014 and, perhaps, beyond:
-    The old batteries have been replaced by new modules;
-    Of the three rate sensor units (RSU), two new ones have been installed and one refurbished unit has been implemented since a new unit would not fit in place;
-    The Science Data Handling & Control Unit, of which the primary channel had failed shortly before the initially scheduled SM4 launch, has been replaced by a new unit.
-    One of the three Fine Guidance Sensor (FGS) units - the FGS2 has been replaced;
-    Three large surface areas where the Multi-Layer Insulation (MLI) had severely degraded over the 19 years in orbit have been replaced by panel type of thermal insulation. Originally, only two replacements were scheduled, however, the astronauts proved to be quick in the tasks of the last EVA day and could accommodate a third area replacement. The removal by EVA of the crippled MLI proved to be tricky, with some pieces free floating into space.

In addition to these replacement tasks, the HST has been equipped at the berthing side with a new soft-capture and docking interface. This device will provide a fixture for a future robotic spacecraft to latch onto for de-commissioning Hubble.

At several points in time during the mission the EVA tasks seemed almost to be a “mission impossible”, however, the ingenuity of the supporting teams on the ground in combination with the versatility of the astronauts led always to resolutions to the problems experienced. The ESA HST team at the GSFC STOCC supported the NASA colleagues efficiently in all tasks related to the ESA hardware, the SADM and SADE. As anticipated, substantial solar array slippages have occurred during the EVA tasks. Where necessary, corrective actions have been commanded in order to maximize the time for EVA activities.

The great cooperation in this ESA/NASA Hubble mission has been a rewarding experience for all team members. This joint team is a real A1-team and the many years of SM4 mission preparations, including contingency procedures development, paid off. SM4 has been fully successful and expectations have been exceeded.

Hubble has now been successfully released into orbit for a new life promising many scientific discoveries. Equipped with new eyes representing most advanced detector capabilities, a new “brain”, stabilisation units and shiny new thermal panels, the telescope appears as a newborn star in orbit.

The ESA HST team says goodbye and good luck to Hubble and a safe return for Atlantis and the great astronauts!

The ESA HST team will follow the Hubble operations until the first solar array slews (turns) have been successfully completed on the in-orbit released telescope.