Update on the launch processing of Gaia (after the rescheduling)

In one of my recent blog entries a few days before the component alarm was raised for the transponders of Gaia I outlined the next steps in the Gaia launch processing: https://hvossgaia.wordpress.com/2013/10/18/next-steps-of-the-gaia-launch-processing/. Due to these defect components a launch delay had to hit the project leading to a rescheduled launch date of Gaia on December 20.  The entire process necessary until the launch of Gaia is more complicated now and includes also the launch of the Ariane 5 ECA (VA216) with two communication satellites. Therefore, I will give an update on the schedule now. Today seven weeks are remaining until the launch of Gaia on December 20 now. Thus, let us go week by week starting with next week.

Week 1: Gaia is still in storage in cleanroom S1B in Kourou. The transponders are in Italy for repair with the potentially defect transducers to be replaced. For the Ariane 5 launch planned for December 6 there should be some progress made. The payloads, the communication satellites Amazonas 4A of HISPASAT and Astra 5B of SES should arrive in French Guiana to start their launch processing. This is usually taking four weeks and includes testing, fueling and the connection with the launcher.

Week 2: During this week the repaired Gaia transponders should arrive at the European launch base in Kourou to be reinstalled in the Service Module of Gaia (see the scheme below). Retesting of the integrated transponders should begin during this week.


Schematic view of the Gaia Service Module showing the location of the transponders in doubt. This module is situated below the Payload Module and both are enclosed by the folded sunshield (Image: ESA/EADS Astrium).

Week 3: The testing of the repaired transponders should have been finished successfully. The entrance to the Service Module of Gaia should be closed as well as the opening in the sunshield of Gaia allowing to access the Service Module despite having the sunshield in the folded launch configuration.

Week 4: Gaia should be back in normal processing mode. It should be moved to the Hazardous Payload Facility of building S5A for the fueling of the Chemical Propulsion System (CPS) with monomethyl hydrazine and mixed nitrogen oxides, and the Micro-Propulsion System (MPS) with nitrogen. 

Week 5: Gaia will be connected to the Payload Adapter System (PAS). This will also take place in building S5A.  On December 6, during the launch window from 21:57 GMT to 23:03 GMT, the Ariane 5 ECA V216 mission needs to lift off to allow Gaia launch on December 20. Any delay here will cause a delay for the Gaia launch, too.

An Ariane 5 lifts off from the European launch base Kourou. ON December 6 something similar should happen to allow a launch of Gaia on December 20.

An Ariane 5 lifts off from the European launch base Kourou. On December 6 something similar should happen to allow a launch of Gaia on December 20.

Week 6: The satellite-PAS system will be connected to the fueled Fregat upperstage in the S3B building of the spaceport. Gaia-PAS-Fregat will be enclosed by the payload fairing forming the so-called Upper Composite. The systems that monitor the launch trajectory of the rockets lifting off from Kourou need to be adopted for the Soyuz-Fregat launch with Gaia. This takes 14 days at least. Was this ever done before? Yes, in 2012. An Ariane 5 lifted off on Sepetember 28, 2012. 14 days later a Soyuz-Fregat with two Galileo spacecrafts was launched. But any significant problem with the adaption of these range systems and the launch of Gaia will need to be delayed.

Week 7: The Upper Composite will be moved to the launch pad by a special transporter. What will happen here will be described in a future blog post. 😉


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