ALBERT

Description: The cryogenic thermal vacuum/thermal balance test of the James Webb Space Telescope (JWST) combined Optical Telescope Element (OTE)/Integrated Science Instrument Module (ISIM), known as the OTIS, at the Johnson Space Center (JSC) Chamber A in 2017 was likely the most complex test ever performed by NASA for an unmanned mission. The test of the combined flight Optical Telescope and ISIM elements was prefaced by years of modifications to chamber facilities, and included three extensive precursor tests of non-flight and flight hardware to establish safe and optimal test operational procedures. One critical part of the test preparation was planning for off-nominal events that could arise, including appropriate responses. In some cases, assurance of personnel and payload safety required modification of original test hardware and procedures which had to be validated before the final test could begin. This planning proved especially prescient for the OTIS test, as Hurricane Harvey struck the Houston area during the test in August 2017, and consequences for the precious payload could have been severe. This paper describes the extent of the thermal off-nominal planning undertaken for the OTIS test, including including safing for hurricanes, and some real-life effects of Hurricane Harvey on the test conduct. Documentation of the consequences and mitigations for these events are discussed. The importance of off-nominal planning for future thermal vacuum/thermal balance tests is illustrated.

Description: The Lunar Atmosphere and Dust Environment Explorer (LADEE) mission launched on September 7, 2013 with a one month cruise before lunar insertion. The LADEE spacecraft is a power limited, octagonal, composite bus structure with solar panels on all eight sides with four vertical segments per side and 2 panels dedicated to instruments. One of these panels has the Lunar Laser Communications Demonstration (LLCD), which represents a furthering of the laser communications technology demonstration proved out by the Lunar Reconnaissance Orbiter (LRO). LLCD increases the bandwidth of communication to and from the moon with less mass and power than LROs technology demonstrator. The LLCD Modem and Controller boxes are mounted to an internal cruciform composite panel and have no dedicated radiator. The thermal design relies on power cycling of the boxes and radiation of waste heat to the inside of the panels, which then reject the heat when facing cold space. The LADEE mission includes a slow roll and numerous attitudes to accommodate the challenging thermal requirements for all the instruments on board. During the cruise phase, the internal Modem and Controller avionics for LLCD were warmer than predicted by more than modeling uncertainty would suggest. This caused concern that if the boxes were considerably warmer than expected while off, they would also be warmer when operating and could limit the operational time when in lunar orbit. The thermal group at Goddard Space Flight Center evaluated the models and design for these critical avionics for LLCD. Upon receipt of the spacecraft models and audit was performed and data was collected from the flight telemetry to perform a sanity check of the models and to correlate to flight where possible. This paper describes the efforts to correlate the model to flight data and to predict the thermal performance when in lunar orbit and presents some lessons learned.