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SwRI Led CYGNSS Assembly, Integration and Testing

SwRI's system testing for CYGNSS verified and validated all elements against their requirements, ensuring system interoperability and providing training for the flight operations team. To reduce risk, a full Engineering Model (EM) Observatory was fabricated, assembled, and tested to assess design requirement compliance, acting as a pathfinder for fabrication and test procedures and ensuring readiness for full testing.This EM Observatory was taken through full Electromagnetic Compatibility (EMC) testing for early indication that CYGNSS would meet EMC requirements.

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Eight Flight Model Observatories were then assembled using the processes learned during the EM build. Assembly order was based on component availability with the only constraint that any activity must be complete on Flight Model 1 Observatory (the fleet leader) prior to being performed on a subsequent Observatory. In general, the build and test order was as follows:

  • Assemble core structure
  • Install core components and electronics
  • Install harness and perform initial electrical tests
  • Install and test communication subsystem, including Universal Space Network compatibility test with the EM and one FM Observatory
  • Install and test the DDMI payload
  • Start bus closeout and perform initial Comprehensive Performance Tests
  • Complete bus closeout to install and test solar arrays
  • Perform mass properties tests and install ballast
  • Prepare for Environmental testing

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All CYGNSS Observatories were integrated within the SwRI Division-15 class 100k Clean-room. (A 10K clean-cabin exists inside the 100K clean-room, but CYGNSS contamination requirements only required the 100k clean room). Eight Observatory work-areas were configured with ESD benches within the cleanroom, and six EGSE racks were shared amongst the eight work areas. Each EGSE rack included a Solar Array Simulator power supply, a NetAquire front end data processor, a Spacecraft Dynamic Simulator workstation, a PXI chassis for EGSE control and power, and an ITOS command and telemetry interface workstation.

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Environmental Testing
The CYGNSS Observatories were tested for self-compatibility, launch loads and operations in a space environment. The EM Observatory and two FM observatories went through full-spectrum EMC testing, and then three FM Observatories went through limited-spectrum EMC testing to demonstrate consistent performance. One FM observatory was tested in the SwRI RF Chamber in a flight-like tether-free configuration for RF self-compatibility.

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Another FM Observatory was taken to the SwRI Mechanical Test Facility for Random Vibe testing for model correlation (all FM Observatories were Random Vibe tested with the Deployment Module in the launch configuration).

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The Observatories were tested in thermal vacuum chambers that replicate the Space environment. One Observatory went through stand-alone Thermal Balance testing for thermal model correlation in SwRIs 4'x4' thermal vacuum chamber, and then all Observatories went through Thermal Vacuum/Thermal Cycling tests, four at a time in SwRI's new 8'x8' thermal-vacuum chamber.

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Flight Segment Integration
After the Observatory-level tests were complete, the Observatories moved to Flight Segment integration where they were mated and tested with the Deployment Module (DM). The Deployment Module was assembled and tested by Sierra Nevada Corporation (SNC) where Observatory Mass Models were installed for DM random vibration testing. Upon delivery to SwRI, the DM again had Mass Models installed by SwRI technicians as a dry-run for flight integration and practice using the Observatory Installation/Separation MGSE. The DM + Mass Model configuration went through pyro-shock testing with support from Orbital ATK, and the DM+Mass Models also went through reduced level random vibe as a facility test and to ring-out the multi-channel data acquisition system.

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After shock and vibration testing with Mass Models, the Mass Models were separated from the DM exercising the separation mechanisms using the same support equipment and processes as used with the Flight Hardware.

The flight Observatories were then integrated with the Deployment Module using the processes and support equipment practiced with the mass models. The integrated flight segment then went through 3-axis random vibration testing before Flight Model Observatories were separated and packed for transport to the launch vehicle integration site.

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Launch Vehicle Integration
The individually packed Observatories, DM and support equipment were shipped to Vandenberg Airforce Base to be integrated with the Orbital/ATK Pegasus XL launch vehicle. All Observatories went through post-ship stand-alone functional testing and solar array deployment prior to being re-integrated with the DM. After Flight Segment functional testing, the flight segment was integrated with the Launch vehicle. Unlike other payloads that are mated with the rocket vertically, the Pegaus XL requires payloads to mated horizontally. Special fixturing was used to lift the CYGNSS flight segment horizontally and to maintain a level orientation as Orbital/ATK technicians bolted the adapter cone to the front of the rocket.

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After CYGNSS was installed on the rocket, all of the vehicle arm plugs were installed, remove-for-flight items were removed, then Orbital/ATK technicians installed the fairing.

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The Pegasus/XL rocket with CYGNSS was rolled out to the VAFB runway, then the rocket was mated with the Orbital/ATK L-1011 "Stargazer."

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The L-1011 then flew from VAFB to Cape Canaveral Airforce Station where the Pegusus XL was air-launched on December 15, 2016.

 

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