jump directly to section navigation jump directly to site level navigation jump directly to content top jump directly to footer information
NASA's EO1 Satellite. Click here for NASA Home Goddard Space Flight Center GSFC
> Earth Sciences Enterprise > New Millenium Program > GSFC > EO-1
+ NASA Portal
+Search NASA Portal

eo1 extended mission main menu eo1 general main menu eo1 baseline mission menu eo1 intranet search the EO1 site eo1 mission home page



goto EO-1 Home Page

Failures & Anomalies  

see the associated EO-1 Validation Report

Related Sites
USGS/EO-1 website at

Questions and comments related to this document should be directed to:

Michael Flick
EO-1 Technology Transfer Manager
EO-1 Mission Office
NASA Goddard Space Flight Center
Greenbelt, MD 20771
Phone: 301-286-8146
Fax: 301-286-1736
E-Mail: Michael Flick

Hyperion Cryocooler Sensor

On 10 January 2001 , there was a failure of the Cryocooler’s compressor motor ‘positive’ direction stroke measurement position sensor. This failure caused the cooler electronics control algorithm to malfunction which ultimately led to a higher than normal temperature signature from the cooler. The Hyperion Cryocooler was operated over several following weeks with an interim work-around to bypass the failed positive stroke sensor whereby the duty cycle was limited to approximately 50% (1 day on, 1 day off) and the maximum drive limit was reduced from 89% to 75% to provide conservative operating margins. Unfortunately, run in this fashion, the cooler was often unable to maintain proper temperature control throughout the late cycle DCE sequences. In addition, this was very operations intensive and required constant monitoring of cryocooler housekeeping data. Some new RTS's were written and tested by TRW which would provide a more efficient solution. They were loaded and operational as of 1/31/01 and provided a permanent fix via a patch to the cooler software. In the new configuration, the cooler attained a proper temperature in roughly the same time (~4 hrs) as prior to the anomaly event and easily maintained that temperature during DCE’s. Shortly after this, another cooler software patch was uploaded to fine tune the RTS’s to allow for near full continuous on-time cooler operation.

The long term consequence of the position sensor failure and corrective action taken by the instrument contractor was to modify the Hyperion operations procedure to perform a Cyrocooler duty cycle turn off every 15 days for a 15 hour period. This procedure allowed the cooler to “de-ice” and therefore regain its normal cooling capability.




SectionNav | SiteNav | PageTop | ContentTop | Footer


NASA Official: Dan Mandl
Curator: Lisa Kane
Webmaster/Design: Steve Sabia
Development: Team List
Security, Privacy, Notices
SectionNav | SiteNav | PageTop | ContentTop