NICMOS STAN +----------------------------------------------------------+ | NICMOS | STScI Analysis Newsletter | 23 January 2009 +----------------------------------------------------------+ Visit the NICMOS web site http://www.stsci.edu/hst/nicmos "New in the Last 45 Days" for all new information about NICMOS. CONTENTS: NICMOS / NCS Status +----------------------------------------------------------+ NICMOS / NCS Status After the previous restart attempt and subsequent safing of the NICMOS Cooling System (NCS) in December 2008, an Anomaly Review Board was convened to examine the failure, which this time was not due to the circulator pump but was instead caused by a low speed limit violation of the Turbo Alternator, which helps to maintain the proper flow rate of coolant. After examination of the data, approval was given by HST Project for a restart attempt on Thursday, 15 January 2009. The system initially restarted nominally, with the circulator pump motor behaving as expected and soon reaching a stable current level of around 62 mA, which it maintained for the next 24 hours. On Friday 16 January 2009, approval was given to proceed with the cooldown phase which involved activating the compressor and Turbo Alternator, this time with modified restart parameters. The cooldown proceeded for about 10 hours until the Turbo Alternator safed, again with a low speed limit violation similar to the signature seen in December 2008. The HST Project has decided to defer subsequent NICMOS Cooling System startup attempts until after Servicing Mission 4, due to limitations on the amount of time remaining. At STScI, the HST Mission Office and the Director's Office were involved in these discussions and support this decision. The NCS Anomaly Review Board is continuing its investigation of the failed restart attempts and will prepare a recommended plan of action for any future restart attempts after SM4. +----------------------------------------------------------+ For more detailed information and updates, please consult the NICMOS webpages: http://www.stsci.edu/hst/nicmos +----------------------------------------------------------+ | Help: help@stsci.edu +----------------------------------------------------------+ | To subscribe or unsubscribe to the STAN, send a message | to majordomo@stsci.edu with the subject line blank and | the following in the body: [un]subscribe nicmos_news +----------------------------------------------------------+ | The Space Telescope Science Institute is operated by the | Association of Universities for Research in Astronomy, | Inc., under NASA contract NAS5-26555. +----------------------------------------------------------+
