IOC Status Archive

Update: 09 December 2003

This update was posted on Tuesday, December 9, the 107th day of the mission. All systems are normal. SIRTF is proceeding with its science mission, with observations taken for the First-Look Survey and the Guaranteed Time Observing programs. Validation observations have also been obtained for the Legacy Science projects. The inaugural MIPS instrument campaign of the science mission began Sunday night (Pacific time) and will continue through Sunday. The first Early Release Observations from SIRTF will be presented at a NASA news conference on Thursday, December 18 at 1:00 pm (EST). The new name for SIRTF will also be announced at that time. The press conference will be televised live on NASA-TV and Webcast at www.nasa.gov/multimedia/nasatv/.

Update: 05 December 2003

This update was posted on Friday, December 5, the 103rd day of the mission. All systems are normal. SIRTF has started its science observing program with the Infrared Array Camera (IRAC), the near- to mid-infrared camera. Observations of the extragalactic portion of the SIRTF First-Look Survey have begun. In addition, various Guaranteed Time Observations proposed by members of the Science Working Group are being executed. The IRAC instrument campaign will continue through Sunday evening (Pacific time). A five-and-a-half day campaign with the Multiband Imaging Photometer for SIRTF (MIPS), the long-wavelength instrument, will then commence. The first Early Release Observations from SIRTF will be presented at a NASA news conference on Thursday, December 18 at 1:00 pm (EST). The new name for SIRTF will also be announced at that time. The press conference will be televised live on NASA-TV and Webcast at www.nasa.gov/multimedia/nasatv/.

Update: 02 December 2003

On this Tuesday, December 2, we celebrate the 100th day of the mission! The in-orbit checkout and science verification period has concluded and the observatory has started its science mission. The first observing program is the First-Look Survey (FLS), conducted by the SIRTF Science Center (SSC) on behalf of the astronomical community. This 110-hour survey is designed provide a characteristic "first-look" at the mid-infrared sky at sensitivities that are 100 times deeper than previous systematic large-area surveys. The SSC will rapidly process the data and place it into the public domain in time to assist scientists in planning their Cycle-1 proposals. It is anticipated that portions of the FLS data will be available to the community by mid-January.

Update: 25 November 2003

This update was posted on Tuesday, November 25, the 93rd day of the mission. Science verification activities continue and all operating systems are normal. A 22-hour IRS campaign started on Saturday morning (Pacific time) and was devoted to diagnostic measurements of the long-low filter and the instrument peakup performance. A 39-hour MIPS campaign began Sunday morning and included validation activities for the scan mapping observing mode, the spectral energy distribution mode, and the photometry mode. We are currently executing a 64-hour IRAC campaign, started early this morning, to measure absolute calibrations. An 11-hour MIPS campaign will start about the time that many will be seated for their turkey dinner on Thanksgiving Day. It will include validation observations for the 24-micron scan mapping observing mode. A 29-hour IRS campaign starts early Friday morning and will include validation activities for the spectral mapping observing mode, measurements of the long-low filter integrity and various peakup diagnostics. A 44-hour MIPS campaign begins on Saturday morning and will include measurements of flux standards, scattered light and the 160-micron array geometry. It will also measure the instrument's confusion limits. The next mission update is scheduled for Monday, December 1 -- the first day of 'normal' science operations!

Update: 21 November 2003

This update was posted on Friday, November 21, the 89th day of the mission. Science verification activities continue and all operating systems are normal. A 62-hour IRAC campaign started on Wednesday night (Pacific time) and included testing of mitigation strategies for latent images, characterization of bright source effects, measurements of the array distortions, and validation of the IRAC observing mode. Starting late Saturday morning, a 22-hour IRS campaign will be devoted to diagnostic measurements of the long-low filter and the instrument peakup performance. A 39-hour MIPS campaign begins Sunday morning and will include validation activities for the scan mapping observing mode, the spectral energy distribution mode, and the photometry mode. It will also feature measurements of celestial flux standards and various engineering tasks. The mission's nominal 90-day in-orbit checkout and science verification phase will be extended for seven days, primarily to account for interruptions caused by solar storms. The science mission is tentatively scheduled to begin on December 1 with the SIRTF First-Look Survey. The next mission update is scheduled for Tuesday, November 25.

Update: 18 November 2003

This update was posted on Tuesday, November 18, the 86th day of the mission. Science verification activities continue and all operating systems are normal. A 74-hour IRS campaign began last Thursday and included spectrophotometric calibrations, characterization of spectral stray light, testing of the long-wavelength/low-resolution filter, and peakup diagnostic measurements. A lengthy series of MIPS observations started on Sunday afternoon (Pacific time) and will conclude on Wednesday evening. These sequences include a wide variety of observations intended to validate the scan mapping observing mode, characterize latent images and saturated sources, characterize the 24 micron point spread function and to measure flux linearities as a function of sky background. A 62-hour IRAC campaign starts on Wednesday night and will include testing of mitigation strategies for latent images, characterization of bright source effects, measurements of the array distortions, and validation of the IRAC observing mode. The next mission update is scheduled for Friday, November 21.

Update: 14 November 2003

This update was posted on Friday, November 14, the 82nd day of the mission. Science verification activities continue and all operating systems are normal. A 15-hour IRAC campaign started on Tuesday morning (Pacific time) and included testing of various latent image mitigation strategies. A subsequent IRAC campaign ended prematurely early Wednesday morning when the observatory entered safe mode. The problem was quickly traced to a flawed configuration file uplinked to the spacecraft. The observatory resumed normal operations on Wednesday afternoon. A 74-hour IRS campaign began at midday Thursday and includes spectrophotometric calibrations, characterization of spectral stray light, testing of the long-wavelength/low-resolution filter and peakup diagnostic measurements. A 17.5 hour MIPS campaign will start on Sunday afternoon and will include engineering observations to assess non-linearities in the electronics and in flux measurements. These activities will be immediately followed by another MIPS campaign, of 63 hours duration. The longer campaign will include a wide variety of observations intended to validate the scan mapping and photometry/super-resolution observing modes, measure flux standards, characterize latent images and saturated sources, and to measure flux linearities. This campaign will continue through Wednesday night. The next mission update is scheduled for Tuesday, November 18.

Update: 11 November 2003

This update was posted on Tuesday, November 11, the 79th day of the mission. Science verification activities continue and all operating systems are normal. A 60-hour MIPS observing campaign was completed on Saturday. It included a wide variety of engineering tasks, including testing/validation of the scan mapping mode and the photometry mode, characterization of off-axis glints, and observations of calibration standards. A subsequent 58-hour IRS campaign was finished early today (Pacific time) and was devoted to flat-field and wavelength calibration activities, and to characterization of peakup offsets. A 48-hour set of IRAC observations is now underway and includes testing of various latent image mitigation strategies and a large number of calibration observations. A 74-hour IRS campaign will begin at midday on Thursday. It includes spectrophotometric calibrations, characterization of spectral stray light, testing of the long-wavelength/low-resolution filter and peakup diagnostic measurements. The next mission update is scheduled for Friday, November 14.

Update: 07 November 2003

This update was posted on Friday, November 7, the 75th day of the mission. Science verification activities continue and all operating systems are normal. The solar storms have subsided, with no significant damage seen in any of the instrument detector arrays. A 60-hour MIPS observing campaign is in progress. It includes a wide variety of engineering tasks, including testing/validation of the scan mapping mode and the photometry mode, characterization of off-axis glints, and observations of calibration standards. A 58-hour IRS campaign will begin Saturday evening (PST) and will be devoted to flat-field and wavelength calibration activities, and to characterization of the peakup offsets. The next mission update is scheduled for Tuesday, November 11.

Update: 04 November 2003

This update was posted on Day 72 of the mission (Tuesday, November 4). The science verification phase of the mission continues. The outer shell temperature remains steady at 34 K, with the telescope primary mirror at 5.7 K. Solar flare activity picked up again over the past weekend. While the observatory continued in normal operations, the higher level of cosmic ray particles yielded a clear (and noisy) signature on MIPS 24-micron data obtained on Sunday. As a result, about 16 hours of engineering tests will be repeated. Within the past 24 hours, validation tests of the MIPS Photomtery/Super-Resolution observing mode have been executed. A 40-hour IRAC campaign is underway and is devoted mostly to observations of primary and secondary calibrators. A 60-hour MIPS campaign will start early Thursday (PST), and include a wide variety of engineering activities. The next mission update is scheduled for Friday, November 7.

Update: 31 October 2003

This update was posted on Day 68 of the mission (Friday, October 31). The science verification phase of the mission has resumed now that the proton flux density from solar coronal mass ejections has diminished to safe levels. The next update is scheduled for Tuesday, November 4.

Update: 30 October 2003

This update was posted on Day 67 of the mission (Thursday, October 30). The science verification phase of the mission remains on hold due to solar storms. The telescope continues cooling towards the operating temperature of 5.5 K, after being warmed slightly by the enhanced solar proton flux earlier in the week. Normal operations could resume within 24 hours.

Update: 29 October 2003

This update was posted on Day 66 of the mission (Wednesday, October 29). Science verification activities remain on hold due to powerful solar storms. The peak temperature of the telescope primary mirror increased by about 2K, probably in response to the substantial increase in proton flux from recent coronal mass ejections. However, the telescope is once again cooling towards its normal operating temperature of 5.5K. Once normal operations resume, SIRTF will execute various tests of the MIPS observing modes.

Update: 28 October 2003

This update was posted on Tuesday, October 28, day 65 of the mission. The 60-day In-Orbit Checkout (IOC) period has formally ended and SIRTF has entered a 30-day Science Verification (SV) period. IOC was intended to demonstrate the functional performance of the observatory, while SV is devoted primarily to characterization of the science observing modes. At the moment, SV activities have been placed on hold, due to the enhanced solar activity.

Update: 24 October 2003

This update was posted on Friday, October 24, day 61 of the 90-day in-orbit checkout and science verification period. A flight software anomaly caused SIRTF to enter "standby" mode early Thursday. The problem, which was not caused by enhanced solar activity, has been resolved. The observatory returned to normal operations mode later in the day. Since the last update three days ago, various MIPS engineering activities have been executed, with emphasis on validation of the scan map capability, a focal plane survey of the 70-micron array, and optimizing the bias for the 70- and 160-micron arrays. Over the next few days, IRS activities will include a focal plane survey and the testing and analysis of peak-up capabilities. The next semi-weekly update will appear on October 28.

Update: 21 October 2003

This is Day 58 of the 90-day in-orbit checkout and science verification period. Tests of the pointing calibration and reference sensor (PCRS) have been completed successfully. The PCRS is a cryogenic optical imager that serves as the observatory's fine guidance sensor by providing an alignment reference between the telescope boresight and the spacecraft attitude detrmination system. Those tests indicate that SIRTF will meet, and perhaps exceed, its pointing requirements. The next update will be provided on Friday, October 24.

Update: 17 October 2003

This is Day 54 of the 90-day in-orbit checkout and science verification period. With the telescope now in focus and at operating temperature, the analysis of engineering data from the two long-wavelength MIPS channels is underway. This image shows the 70-micron point spread function, based on data obtained from a 2 Jy star. The next update will be posted on October 21.

Update: 15 October 2003

This is Day 52 of the 90-day in-orbit checkout (IOC) and science verification (SV) period. The telescope has reached its operating temperature of 5 K (minus 451 degrees F.) and the focus adjustments have been completed (see archived IRAC, IRS, and MIPS focus images). With the telescope now sufficiently cold, the initial data from the MIPS 70- and 160-micron channels have been obtained. For the balance of the IOC/SV phase of the mission, web updates will appear semi-weekly.

Update: 10 October 2003

This is Day 47 of the 90-day in-orbit checkout and science verification period. All systems continue to perform as expected. An image taken with the MIPS 24 micron array after final focusing of the telescope is available here (see also the IRS and IRAC images). During focusing, the secondary mirror was commanded closer to the primary mirror by 16.4 microns (0.00065 in.), about one-sixth the thickness of a sheet of paper. For comparison, the distance between the primary and secondary mirrors decreased by 1.16 mm (0.046 in.) as SIRTF cooled from 300 K to 5 K, due to the well-known thermal contraction of beryllium. This thermal contraction, plus changes expected for operation in a zero-g environment, were taken into account in positioning the secondary mirror before launch. As a result, only a small adjustment was required.

Update: 09 October 2003

This is Day 46 of the 90-day in-orbit checkout and science verification period. In-orbit checkout activities continue. All systems are performing as expected. An image taken with the IRS peakup array after final focusing of the telescope last weekend is available here (see also the IRAC images here).

Update: 08 October 2003

This is Day 45 of the 90-day in-orbit checkout and science verification period. The SIRTF telescope was placed in final focus over the weekend. Point source images obtained by the IRAC instrument following the focusing are available here.

Update: 06 October 2003

This is Day 43 of the 90-day in-orbit checkout and science verification period. SIRTF is in focus, and cold! Telescope performance meets or exceeds all requirements for image quality. The telescope temperature is now below 5.5 K, the design temperature and the temperature required for observations at 160 microns. Some parts of the cold telescope assembly are still cooling and will not reach steady-state for another week or two, but achievement of 5.5 K on the telescope itself is an important milestone for SIRTF.

Update: 03 October 2003

This is Day 40 of the 90-day in-orbit checkout and science verification period. The telescope has cooled to below 15 K (-433 F). The first of three scheduled changes in the position of the secondary mirror has been completed. Images taken after the move showed exactly the expected effects. Focus activities continue as planned. The next update will be posted on Monday, October 6.

Update: 02 October 2003

This is Day 39 of the 90-day in-orbit checkout and science verification period. The telescope has cooled to below 20 K (-424 F). Engineering activities related to the assessment and possible adjustment of the telescope focus are proceeding as planned.

Update: 01 October 2003

This is Day 38 of the 90-day in-orbit checkout and science verification period. The telescope has cooled to below 23 K (-418 F). All systems continue to perform as expected.

Update: 30 September 2003

This is Day 37 of the 90-day in-orbit checkout and science verification period. Various engineering activities are leading up to the telescope focus adjustments, scheduled for later this week. All systems are performing as expected.

Update: 29 September 2003

This is Day 36 of the 90-day in-orbit checkout and science verification phase. The telescope is now below 29 K, and a long series of activities is underway whose purpose is to assess and, if necessary, adjust the position of the secondary mirror for best telescope focus in the cold, zero-g operating environment of space. All systems continue to perform as expected.

Update: 26 September 2003

This is Day 33 of the 90-day in-orbit checkout and science verification phase. The telescope is now below 35 K. The first test observations with the Multiband Imaging Photometer for SIRTF (MIPS) at 24 microns were completed successfully. All parts of the system, including the MIPS cryogenic scan mirror and the pointing of the SIRTF telescope, worked well together. The next update will be on Monday, 29 September 2003.

Update: 25 September 2003

This is day 32 of the 90-day in-orbit checkout and science verification period. All systems continue to perform as expected. The relative positions of the IRS peakup imaging arrays and spectrograph slits have been determined accurately. Movements between the short low slit and the short wavelength peakup array have been tested and work very well.

Update: 24 September 2003

This is day 31 of the 90-day in-orbit checkout and science verification period. Instrument checkout and calibration activities continue, punctuated by periodic spacecraft pointing system calibrations. The cooldown is proceeding uneventfully, with both the primary and the secondary mirror below 40K. During the past few days, four of SIRTF's seven Astronomical Observing Templates (AOTs) -- which define different ways in which SIRTF can make scientfic observations -- have been exercised on orbit. These are the IRAC mapping AOT, the IRS staring and spectral mapping AOTs, and the MIPS photometry AOT. In each case, the spacecraft responded appropriately to the AOT commands. For more information about the SIRTF AOTs, see http://ssc.spitzer.caltech.edu/obs/aots.html.

Update: 23 September 2003

This is Day 30 of the 90-day in-orbit checkout and science verification period. Instrument checkout and calibration activities continue. Initial wavelength calibration observations for the InfraRed Spectrograph short/low module have been completed. InfraRed Array Camera observations are being used to calibrate the geometry of the two-dimensional detectors. The small-scale and rapid variation of telescope pointing with time, called jitter, has been measured, and is well within the requirement.

Update: 22 September 2003

This is Day 29 of the 90-day in-orbit checkout and science verification period. The telescope temperature is now below 43 K (-230 C), and the outer shell of the cold telescope assembly is below 37 K (-236 C). The first SIRTF observations of a moving target were made by the InfraRed Array Camera, and are being calibrated and analyzed. All systems continue to perform as expected.

Update: 19 September 2003

This is Day 26 of the 90-day in-orbit checkout and science verification period. Science instrument checkout activities continue. The InfraRed Array Camera completed over three days of continuous operation. All systems continue to perform as expected. The next update will be provided on Monday, 22 September.

Update: 18 September 2003

This is Day 25 of the 90-day in-orbit checkout and science verification period. Science instrument checkout activities continue. The relative positions of the various imaging arrays and spectrograph slits are being determined with increasing accuracy as part of a planned process extending over many weeks. All systems continue to perform as expected.

Update: 17 September 2003

This is Day 24 of the 90-day in-orbit checkout and science verification period. In-orbit checkout activities continue as planned. The observatory has operated autonomously, collecting and downlinking data, for periods in excess of 24 hours. All systems are performing as expected. Engineering data from the science instruments are flowing smoothly from the spacecraft through the ground data system to the pipeline at the SIRTF Science Center, which is processing the data as planned. The telescope is now at about 53 K (-220 C), and is expected to reach its nominal operating temperature of 5.5 K (-267.5 C) in early October.

Update: 16 September 2003

This is Day 23 of the 90-day in-orbit checkout and science verification period. The telescope continues to cool as expected. The mirrors are now below 55 K (-218 C) and the outer shell of the cold telescope assembly is below 40 K (-233 C). At these temperatures, both radiation to space and conduction into the helium vapor leaving the cryostat are important mechanisms for removing heat from the telescope. As temperatures fall, radiation becomes steadily less effective, and most of the cooling is provided by the helium vapor. The SIRTF instruments by themselves dissipate too little power into the cryostat to produce the necessary amount of helium vapor. Accordingly, as planned, a small heater has been turned on to supplement the instrument power. All systems continue to perform as expected.

Update: 15 September 2003

This is Day 22 of the 90-day in-orbit checkout and science verification period. Checkout of the three science instruments continues. The PCRS (28 August) was used to point SIRTF accurately at a star, which was then imaged with the IRS (12 September) 15-micron imaging array. The star was centered on the entrance slit of the IRS short/low module, which covers from 5.5 to 15 microns, and the first engineering spectrum was taken by SIRTF. All parts of the system worked well together. Telescope thermal emission still dominates at the longer wavelengths. The first data downlinks with the high gain antenna (14 September) at 2.2 Mbs proceeded as planned.

Update: 14 September 2003

This is Day 21 of the 90-day In-Orbit Checkout and Science Verification period. SIRTF is now about 2 million kilometers (1.2 million miles) from Earth. The high gain antenna was used for the first time to communicate with the ground system. This antenna, similar to a small satellite TV dish, concentrates signals from SIRTF in a narrow cone, allowing data to be sent at a rate 25 times higher (2.2 Mbs vs. 88 kbs) from far away. From now until the end of the science verification period SIRTF will remain in constant contact with the ground through the near-omnidirectional low gain antennas, switching to the high gain antenna to downlink the large volumes of data generated by the science instruments. The telescope has cooled to below 60 K (-213 C), and the outer shell of the cold telescope assembly has cooled to below 40 K (-233 C), as expected.

Update: 13 September 2003

This is Day 20 of the 90-day In-Orbit Checkout and Science Verification period. Instrument and subsystem checkout activities continue as planned. The "pipeline" processing system at the SIRTF Science Center is handling all instrument data smoothly. All systems are performing as expected.

Update: 12 September 2003

This is Day 19 of the 90-day In-Orbit Checkout and Science Verification period. The InfraRed Spectrograph (IRS) was turned on for the first time in space. All detector arrays are working as expected. Emission from the telescope still strongly dominates most of the wavelength range of the IRS, as expected. The telescope has cooled to about 65 K (-208 C), and the outer shell of the cold telescope assembly (which surrounds the telescope and cryostat) has cooled to about 40 K (-233 C). All systems continue to perform as expected.

Update: 10 September 2003

This is Day 17 of the 90-day In-Orbit Checkout and Science Verification period. The infrared array camera and multiband imaging photometer (see update 2 September) checkout and calibration activities continue as planned. The telescope continues to cool. The primary mirror is now below 70 Kelvin (-197 Celsius), cold enough that images at 3.6, 4.5, and 5.8 microns are largely free of thermal emission from the telescope. Images at 8.0, 24, and 70 microns are still strongly affected by telescope emission, as expected. Initial turn-on of the infrared spectrograph (IRS) is scheduled for later this week.

Update: 08 September 2003

This is Day 15 of the 90-day In-Orbit Checkout and Science Verification period. All systems continue to perform as expected. Initial calibration of the pointing control system was completed successfully over the weekend, and all components of the system, including star trackers, gyroscopes and the pointing control reference sensor, or PCRS, (see update 28 August) are working together as expected to point SIRTF accurately at the commanded position on the sky.

Update: 05 September 2003

This is Day 12 of the 90-day In-Orbit Checkout and Science Verification period. All systems continue to perform as expected. Calibration of the pointing control system is underway. The next update will be posted on Monday, September 8.

Update: 04 September 2003

This is Day 11 of the 90-day In-Orbit Checkout and Science Verification period. The observatory remains in normal operating mode and all systems are performing as expected. In-orbit checkout activities continue as planned.

Update: 03 September 2003

This is Day 10 of the 90-day In-Orbit Checkout and Science Verification period. The observatory is operating in normal mode, with all systems performing as expected. NASA has released an initial "aliveness test" image taken with the Infrared Array Camera short-wavelength array. For additional details, visit the online News Room.

Update: 02 September 2003

This is Day 9 of the 90-day In-Orbit Checkout and Science Verification period. The Observatory is in "normal mode," and all systems are performing as expected. Instrument checkout continues. The Infrared Array Camera (IRAC) and Multiband Imaging Photometer for SIRTF (MIPS) have been powered on.

Update: 01 September 2003

This is Day 8 of the 90-day In-Orbit Checkout and Science Verification period. Following ejection of the Dust Cover and opening of the Aperture Door, the Observatory was commanded out of safe mode. In-orbit checkout continues.

Update: 31 August 2003

This is Day 7 of the 90-day In-Orbit Checkout and Science Verification period. The Aperture Door (see update 28 August) has been opened!

Update: 30 August 2003

This is Day 6 of the 90-day In-Orbit Checkout and Science Verification period. The Observatory Dust Cover (see update 28 August) has been ejected successfully!

Update: 29 August 2003

This is Day 5 of the 90-day In-Orbit Checkout and Science Verification period. Reaction wheel #2 was reactivated following warmup (see 28 August update), and was used in combination with the other three wheels to rotate the Obsevatory. Performance was good. Internal friction or drag torque has decreased with increasing temperature, as expected. SIRTF continues in safe mode in preparation for Dust Cover Ejection and Aperture Door Opening this weekend. All systems are working well.

Update: 28 August 2003

This is Day 4 of the of the 90-day In-Orbit Checkout and Science Verification period. SIRTF remains in safe mode as heaters raise the temperatures of the reaction wheels (see update for 27 August 2003) to their nominal operating range. The behavior of the wheels at low temperatures is consistent with characterization measurements made before delivery. The wheel that was turned off will be reactivated when the warmup is complete. The first test of the Pointing Calibration and Reference Sensor (PCRS) system was completed successfully. The PCRS provides fine pointing control for the Observatory by centering up on stars or other unresolved objects whose positions are known accurately. This initial PCRS test measured performance with no light from the sky (i.e., "in the dark") with both the dust cover and the aperture door cover still in place. [The former closes the end of the telescope during ground operations and launch, and the latter seals the cryostat during those same periods.] All PCRS pixels are good. Recovery from cosmic ray hits is excellent. Noise is lower in space than seen on the ground, as expected. This is the first test of a SIRTF instrument in space. The telescope and primary mirror have cooled to approximately 200 Kelvin (about -70 C or -100 F) with the temperature profile following model predictions nicely. In summary, SIRTF is a very healthy spacecraft.

Update: 27 August 2003

This is Day 3 of the 90-day In-Orbit Checkout and Science Verification period. Initial checkout of the pointing and control system has been completed. Pointing performance meets expectations, and pointing stability or "jitter" over a 10-minute period is excellent. During a test of the reaction wheel system, which controls the orientation of SIRTF, one of four reaction wheels was unable to supply the requested torque. (Only three reaction wheels are required to operate SIRTF; any one of the four can be regarded as redundant.) The fault protection system responded correctly by turning off that wheel and putting SIRTF in safe mode. Preliminary analysis suggests that this is a temperature effect. Friction internal to reaction wheels, called "drag torque," increases at low temperature, affecting some wheels more than others, and the temperature of the wheel in question is now at its minimum for the mission. When the science instruments are turned on, its temperature will rise. Additional analysis is in progress. All other SIRTF systems are operating very well, both on the spacecraft and with the teams at NASA's Jet Propulsion Laboratory and the California Institute of Technology, both in Pasadena, and Lockheed Martin Astronautics in Denver.

Update: 26 August 2003

Initial operations have gone very smoothly. The expected post-launch rise in helium bath temperature is approaching turnaround slightly and comfortably below the predicted maximum value, and all aspects of cryo performance look good. Initial position acquisition with the star tracker soon after separation from the rocket was precluded by high background light level near the Earth. This possibility had been anticipated, and a contingency plan that involved position acquisition by the coarse Sun sensors, entry to safe mode, star tracker acquisition, exit to standby mode, and then normal operations proceeded smoothly. The star tracker is working perfectly in "window track mode." Pointing and engineering data are flowing smoothly from the spacecraft all the way to the SSC database.

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