04 Mar 2009 15:17

Alignment measurements

Over the course of past week the spacecraft alignment stability tests were performed to verify the mechanical stability of the spacecraft. These tests included the alignment measurements of the service module, the payload module, and the spacecraft thrusters attached to the service module. For the payload module alignment measurements, the telescope cover, as well as the small focal plane unit (FPU) cover (protecting the HFI feed horns), were removed.

Spacecraft alignment measurements, 23 February 2009. Credit: ESA/Thales	Installing the alignment tool on a 20 N thruster, 25 February 2009. Credit: ESA/Thales

The FPU cover was removed on the morning of 26 February in preparation for the final FPU alignment measurement. This provided a nice photo opportunity to see the telescope and the uncovered instruments' focal plane units.

Left: Removing the Planck telescope's hard cover, 26 February 2009. Credit: ESA/Thales Top right: View of the telescope cavity after removal of the cover, revealing the primary and secondary mirror and the FPU. Credit: ESA/Thales Lower right: Shortly after, the FPU cover was also removed. Credit: ESA-CNES-Arianespace / Optique Vidéo du CSG – L. Mira

Some more nice views of the uncovered telescope on 26 February:

Left: Reflection of the Herschel spacecraft in the Planck primary mirror. Credit: ESA Above: The HFI and LFI feedhorns on the focal plane box, seen reflected in the primary mirror. Credit: ESA/Thales

Above: Planck, secured to its multi-purpose trolley, is put in a vertical position after removal of the telescope cover and the FPU cover. Credit: ESA-CNES-Arianespace / Optique Vidéo du CSG - L. Mira

Functional tests

Earlier in the week, on 24 February, the Planck spacecraft was switched on for the first time at CSG, initiating the main series of functional tests. The required electrical ground support equipment, including the specific check-out equipment (SCOE) for the different subsystems of the spacecraft, had been installed in the S1B clean room on the preceding days.

The first functional tests to be completed were the payload module System Integration Test (a functional test of the scientific instruments) and the ESOC "listen-in" on the Network Data Interface Unit (NDIU) - this unit was installed in the S1B building with Planck. The "listen-in" test was to verify the simulated link between the spacecraft and the mission control system at Planck's mission operations centre in ESA's European space operations centre (ESOC) in Darmstadt, Germany.

This week and next week, the functional tests will verify, among other systems, the spacecraft subsystems dealing with power control, thermal control, attitude control & measurement, command & data management, and tracking & telemetry.

Solar array integration

On Friday 27 February, Planck's outer part of the solar array was integrated with the spacecraft. Planck's solar array comprises a circular inner part and a ring-shaped outer part that is composed of four quarter sections. The inner part of the array was already installed on the service module at the end of last year when the spacecraft was at Centre Spatial de Liège, Belgium.

The four sections of the outer part of the array were prepared on tables next to the spacecraft inside the S1B clean room and, one-by-one, integrated with the spacecraft, while it was in a vertical position on its multi-purpose trolley. Fully installed at the base of the service module, the complete solar array now has an area of 13 m² and will provide the spacecraft with electrical power once in space.

Top-to-bottom, left-to-right: Integration of the first quarter section of the solar array's ring-shaped outer part, on 27 February. Credit: ESA-CNES-Arianespace / Optique Vidéo du CSG – P. Baudon
Left-to-right, top-to-bottom: Integration of the third quarter section of the solar array's ring-shaped outer part, on 27 February. Credit: ESA