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<\/p>\nFour months after standing down launch operations of the ICON mission on their Pegasus rocket, Northrop Grumman Innovation Systems is entering the home stretch for a realigned launch on 26 October 2018 at 04:05 EDT (0805 UTC) over the Atlantic Ocean off the coast of Cape Canaveral, Florida.<\/p>\n
This week, Northrop Grumman Innovation Systems managers for both ICON and Pegasus sat down with NASASpaceflight\u2019s Chris Gebhardt to discuss what happened back in June as well as the current status of both vehicles in the final weeks before launch.<\/p>\n
What happened in June:<\/b><\/p>\n
In June, Northrop Grumman Innovation Systems (NGIS) began the ferry flight of their Stargazer L-1011 aircraft \u2013 with the Pegasus rocket safely encapsulating ICON inside its payload fairing \u2013 across the Pacific Ocean from California to the Kwajalein Atoll, where the air-drop launch of ICON was set to occur.<\/p>\n
During the first leg of this trip from California to Hawai\u2019i, systems engineers aboard Stargazer noticed an off-nominal reading from one of Pegasus\u2019 new Actuator Control Units.<\/p>\n
\u201cThis is the first time that we\u2019re using Northrop Grumman-designed Actuator Control Units,\u201d stated Bryan Baldwin, Pegasus Program Manager, Northrop Grumman Innovation Systems, in an exclusive interview with NASASpaceflight.<\/p>\n
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Pegasus, with ICON encapsulated inside, in final checkouts before being mated to the Stargazer L-1011 in May 2018. (Credit: L2)<\/p>\n
According to Mr. Baldwin, the previous versions of the Actuator Control Units were installed after ferry flights to the launch location because they couldn\u2019t be powered up prior due to their use of thermal batteries.<\/p>\n
\u201cThis new unit allows us to power up the electronics separately from the actuators, and so we were actually monitoring the system on the ferry flight over [when] we would not have done [that with the older units].\u201d<\/p>\n
NASA educational resources (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n With this real-time monitoring, all was reporting well prior to the start of the ferry flight, but over the Pacific between California and Hawai\u2019i, an off-nominal condition presented.<\/p>\n \u201cThese are actuators that control the fins [on Pegasus], and part of the feedback loop is a potentiometer that senses the position of the fin,\u201d stated Mr. Baldwin. \u201cAnd as we were flying over to Hawai\u2019i, the guys were monitoring the system and noticed that there were some position errors showing up on one of the fins.\u201d<\/p>\n This movement of a fin is not possible during ferry flight because the fins are locked in place. Yet the telemetry coming from the Actuator Control Unit said the fin was moving.<\/p>\n Close-up of a fin on Pegasus, taken after the rocket was mated to the underside of Stargazer in May 2018. (Credit: L2)<\/p>\n After landing as scheduled in Hawai\u2019i, the teams began troubleshooting and tried to duplicate the issue. After a few attempts, they were able to do so, and a review of the data combined with years of experience with Pegasus\u2019 43 flights to date showed a need to stand down launch operations and return to California for additional tests and repairs.<\/p>\n \u201cBased on the fact that this part was flight critical in the control loop for the fin, we had a condition that we couldn\u2019t accept. So we decided that we needed to fly back and do some troubleshooting and replacement,\u201d explained Mr. Baldwin.<\/p>\n After Stargazer\u2019s return to California, the team found contamination in the Actuator Control Unit that was sending the erroneous readings during the ferry flight. NGIS engineers then tested similar parts from newer builds of Actuator Control Units and were able to verify that those newer parts did not have the same contamination issue.<\/p>\n Those newer parts were installed into Pegasus, and system re-tests showed a fully-functioning system \u2013 leading to a clearance to proceed toward launch operations at the end of the month.<\/p>\n During this four month stand down, however, very little had to be done with ICON (Ionospheric Connection Explorer) itself, explained Dave Oberg, Program Manager for ICON, Northrop Grumman Innovation Systems.<\/p>\n \u201cCertainly the top of the list [has been] to keep an active purge on the instruments. Contamination control is one of our primary concerns, and the instruments are very sensitive to that. So we\u2019ve kept an active purge on the instruments.<\/p>\n![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2018\/10\/4C0EBC3A-470E-4F28-B089-197A8C514BF4.jpeg\")
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