Gaia : A Success Story
Gaia is a European Space Agency (ESA) “Cornerstone” mission with a value around $1 billion. Materion Barr Precision Optics & Thin Film Coatings contributed to this major event by providing large, precision filters for two (the Photometer and Radial Velocity Spectrometer - RVS) of the science instruments in the Gaia PayLoad Module (PLM). Gaia’s task over its three year mission will be to perform a “galactic census” which will catalog the precise three dimensional location and other astronomically significant characteristics of about one billion stars. This data will be used for a range of scientific endeavors including detailed information regarding exoplanet locations used by ground-based and space-based science teams.
(Photo credit: European Space Agency)
Materion managed both projects and produced the special coatings in our Westford, Massachusetts facility. The RVS filter is a large format (approximately 8.5 x 7 inches) precision optic with very challenging surface figure and spectral requirements. The flatness required is less than 20 nm deviation from a perfect plane, no easy achievement to fabricate or measure. During its development, the Gaia team comprised of Materion and EADS Astrium, the prime contractor, resolved a number of fabrication and measurement issues that ultimately achieved a filter substrate with superior surface figure. Various subcontractors handled polishing and metrology tasks that also contributed to its success.
One of the challenges of the project involved the discovery of a critical anomaly after the flight filter was installed and tested at the system level. Earlier, Materion’s Westford facility designed, developed, deposited and tested the coatings. Three filters were delivered – a Breadboard Model, Engineering Model (EM) and Flight Model (FM). Even with comprehensive testing of all three filter models over the two years of development, an anomaly was uncovered that could cause a degradation of the image quality of the RVS spectra and harm the science return. Materion was notified in late May 2012 and asked to collaborate in a resolution to this problem and readily agreed.
In the course toward a solution, multiple Materion parties participated in the discussions. Tom Mooney, Product Engineering Manager, and Dave Harrison, Project Manager from Westford, Massachusetts, Mike Zasowski, Director, Marketing & Business Development from Buffalo, New York and Stuart Lawson, Sales Manager - EMEA and India, from the UK / European office visited the Gaia Program Manager and other senior players at ESA / ESTEC in the Netherlands. An initial recovery plan was agreed upon and staff from ESA and Astrium visited Westford to identify the probable cause of the anomaly.
With the help of Astrium and ESA, Materion identified the probable cause of the anomaly and formalized a corrective plan. It was determined that the (spare) EM filter had to be re-polished to perfect flatness before re-coating with a modified deposition process. During the polishing task, test coatings were prepared in order to confirm the cause of the anomaly and demonstrate the Materion ‘fix’. It would then require testing and delivery within a critical time window, as on-going environmental testing would be interrupted to install it. Everything needed to occur on schedule or the launch would be delayed – at tremendous cost.
A number of people contributed to the successful outcome. Zygo of Middlefield, CT delivered a pristine re-worked optic on schedule. Brendan Connell, Export Control Manager, expedited government export documentation. Rob Gomeau, VP of Operations and Materion’s Westford OPS team ensured that the manufacturing and test resources were immediately available. George Allen, Senior Applications / Design Engineer managed the on-going project. The support of Materion’s management at Westford, particularly Robert Naranjo, VP SBU (Strategic Business Unit) was invaluable in clearing the decks and giving the project highest priority.
(Photo Credit: EADS Astrium, France)
In the end, the filter was hand-carried through the labyrinth of customs and TSA in the US and French customs in Toulouse and delivered to Astrium where it was inspected and accepted. The delivered filter had a measured wave front error (a measure of the flatness of the substrate, coating uniformity and homogeneity of the substrate material) of 19 nanometers (billionths of a meter), over the full aperture. This is a variation in flatness equivalent to about 200 atoms. Wavelength variation over the full surface was less than 1nm (thickness variation of about 1 part in 900). The filter met, and in many cases far exceeded, the spectral requirements.
The re-worked filter is now installed in the RVS and the fully integrated PLM has been tested and has passed all specifications. Materion’s work was praised by ESA agency-wide. Among the comments in the ESA Bulletin: “…the filter exhibited excellent spectral and wavefront performance.” This is an example of a broad-based coordinated team effort between Materion and their customers working together on a very short timeline with great success.
Gaia will soon be integrated with the Service Module and in turn with the launch vehicle. An August 2013 launch from Kourou, French Guiana on a Russian/French vehicle is currently scheduled.
For more information, contact Tom Mooney, Product Engineering Manager – Westford at Thomas.Mooney@Materion.com