STScI Logo

Hubble Space Telescope
NICMOS Thermal History

The temperature of the NICMOS detectors is an important calibration parameter. The detectors show a number of effects which are dependent on the thermal environment. Most of these effects can, however, be removed through standard calibration, making it important to maintain the temperature as stable as possible over long time scales.

The temperature of the NICMOS dewar and its detectors is presently monitored using the NIC1 mounting cup sensor. This sensor is located behind the NIC1 camera array and is essentially a diode, with an operating temperature limit of 78K. The temperature is read-out every 30 seconds and is part of the normal HST engineering telemetry.

NICMOS thermal history can be divided into two distinct epochs. It was initially cooled to ~61K by a cryogenic dewar containing solid nitrogen. The cryogenically cooled dewar suffered a shorter lifetime than expected due to a thermal short, leading to a faster sublimation of the nitrogen. Following nitrogen exhaustion in January 1999, the NICMOS instrument warmed up to a temperature of around 260K. As this was much too warm for any useful science observations, NICMOS stayed dormant until the third Servicing Mission in March 2002 when a mechanical cooling machine, using a closed-loop reverse-Brayton cycle, was installed. The dewar temperature is regulated by the new NICMOS Cooling System (NCS) and is used to maintain the detectors at 77.15K, about 15K warmer than with the solid nitrogen cooling.

Operations during the first epoch, with solid nitrogen as the coolant, the detector temperature slowly increased from 61K to 62.5K from the start until right before nitrogen exhaustion. This variation in operating temperature made it necessary to obtain calibration data, i.e. darks, flats and photometric calibration, quite frequently to keep up with the changing thermal environment. During the NCS era, the dewar temperature is higher but also significantly more stable. Temperature variations over the time period March 2002 until the present is less than ~0.1K. Occasionally, there are temperature fluctuations with larger amplitudes, mostly associated with unusually long orbit day time, i.e. the time of the orbit that HST spends in sunlight, combined with the overall solar insolation (maximum in January and minimum in July). More information can be found in the NICMOS ISR 2006-004.

Below we give the temperature, as measured with the NIC1 mounting cup sensor, in monthly and yearly periods for both epochs, starting in March 1997.

Date Data Plot Notes
Oct 2007 ndwtmp11_2007oct.jpg
Sep 2007 ndwtmp11_2007sep.jpg
Aug 2007 ndwtmp11_2007aug.jpg
Jul 2007 ndwtmp11_2007jul.jpg
Jun 2007 ndwtmp11_2007jun.jpg
May 2007 ndwtmp11_2007may.jpg
Apr 2007 ndwtmp11_2007apr.jpg
Mar 2007 ndwtmp11_2007mar.jpg
Feb 2007 ndwtmp11_2007feb.jpg
Jan 2007 ndwtmp11_2007jan.jpg
Dec 2006 ndwtmp11_2006dec.jpg
Nov 2006 ndwtmp11_2006nov.jpg
Oct 2006 ndwtmp11_2006oct.jpg
Sep 2006 ndwtmp11_2006sep.jpg
Aug 2006 ndwtmp11_2006aug.jpg
Jul 2006 ndwtmp11_2006jul.jpg
Jun 2006 ndwtmp11_2006jun.jpg
May 2006 ndwtmp11_2006may.jpg
Apr 2006 ndwtmp11_2006apr.jpg
Mar 2006 ndwtmp11_2006mar.jpg
Feb 2006 ndwtmp11_2006feb.jpg
Jan 2006 ndwtmp11_2006jan.jpg
Dec 2005 ndwtmp11_2005dec.jpg
Nov 2005 ndwtmp11_2005nov.jpg
Oct 2005 ndwtmp11_2005oct.jpg
Sep 2005 ndwtmp11_2005sep.jpg
Aug 2005 ndwtmp11_2005aug.jpg
Jul 2005 ndwtmp11_2005jul.jpg
Jun 2005 ndwtmp11_2005jun.jpg
May 2005 ndwtmp11_2005may.jpg
Apr 2005 ndwtmp11_2005apr.jpg
Mar 2005 ndwtmp11_2005mar.jpg
Feb 2005 ndwtmp11_2005feb.jpg
Jan 2005 ndwtmp11_2005jan.jpg
Dec 2004 ndwtmp11_2004dec.jpg
Nov 2004 ndwtmp11_2004nov.jpg
Oct 2004 ndwtmp11_2004oct.jpg
Sep 2004 ndwtmp11_2004sep.jpg
Aug 2004 ndwtmp11_2004aug.jpg
Jul 2004 ndwtmp11_2004jul.jpg
Jun 2004 ndwtmp11_2004jun.jpg
May 2004 ndwtmp11_2004may.jpg
Apr 2004 ndwtmp11_2004apr.jpg
Mar 2004 ndwtmp11_2004mar.jpg
Feb 2004 ndwtmp11_2004feb.jpg
Jan 2004 ndwtmp11_2004jan.jpg
Dec 2003 ndwtmp11_2003dec.jpg
Nov 2003 ndwtmp11_2003nov.jpg
Oct 2003 ndwtmp11_2003oct.jpg
Sep 2003 ndwtmp11_2003sep.jpg
Aug 2003 ndwtmp11_2003aug.jpg
Jul 2003 ndwtmp11_2003jul.jpg
Jun 2003 ndwtmp11_2003jun.jpg
May 2003 ndwtmp11_2003may.jpg
Apr 2003 ndwtmp11_2003apr.jpg
Mar 2003 ndwtmp11_2003mar.jpg
Feb 2003 ndwtmp11_2003feb.jpg
Jan 2003 ndwtmp11_2003jan.jpg
Dec 2002 ndwtmp11_2002dec.jpg
Nov 2002 ndwtmp11_2002nov.jpg
Oct 2002 ndwtmp11_2002oct.jpg NICMOS suspended on day 289.
Sep 2002 ndwtmp11_2002sep.jpg
Aug 2002 ndwtmp11_2002aug.jpg
Jul 2002 ndwtmp11_2002jul.jpg NICMOS suspended on day 204.
Jun 2002 ndwtmp11_2002jun.jpg NICMOS suspended on day 170.
May 2002 ndwtmp11_2002may.jpg Temperature setpoint adjustment from day 116 to 130.
Apr 2002 ndwtmp11_2002apr.jpg Data missing as a result of the Servicing Mission, which included installation of the NICMOS Cooling System. NICMOS Cooling System started around day 76.
Dec 1998 ndwtmp11_1998dec.jpg NICMOS suspended on days 348 and 358.
Nov 1998 ndwtmp11_1998nov.jpg
Oct 1998 ndwtmp11_1998oct.jpg
Sep 1998 ndwtmp11_1998sep.jpg
Aug 1998 ndwtmp11_1998aug.jpg
Jul 1998 ndwtmp11_1998jul.jpg
Jun 1998 ndwtmp11_1998jun.jpg
May 1998 ndwtmp11_1998may.jpg NICMOS safed/suspended on day 129.
Apr 1998 ndwtmp11_1998apr.jpg NICMOS suspended on day 97.
Mar 1998 ndwtmp11_1998mar.jpg NICMOS suspended on day 75.
Feb 1998 ndwtmp11_1998feb.jpg NICMOS suspended on day 54.
Jan 1998 ndwtmp11_1998jan.jpg NICMOS suspended on day 17.
Dec 1997 ndwtmp11_1997dec.jpg
Nov 1997 ndwtmp11_1997nov.jpg
Oct 1997 ndwtmp11_1997oct.jpg
Sep 1997 ndwtmp11_1997sep.jpg NICMOS suspended on day 270.
Aug 1997 ndwtmp11_1997aug.jpg Continuous detector auto-reset implemented around day 235.
Jul 1997 ndwtmp11_1997jul.jpg
Jun 1997 ndwtmp11_1997jun.jpg
May 1997 ndwtmp11_1997may.jpg
Apr 1997 ndwtmp11_1997apr.jpg End of post-installation activities.
Mar 1997 ndwtmp11_1997mar.jpg NICMOS post-installation activities.
2005 ndwtmp11_2005.jpg
2004 ndwtmp11_2004.jpg
2003 ndwtmp11_2003.jpg
2002 ndwtmp11_2002.jpg
1998 ndwtmp11_1998.jpg
1997 ndwtmp11_1997.jpg