Table of Contents

SCISAT Mission status update

February 11 to February 19, 2004

• Science data continues to be collected routinely during sunset occultations, which give measurements over the Northern hemisphere, and at periods of "high sun" during which sun scans give reference spectra.
• The FTS detectors are undergoing decontamination cycles, as necessary, to keep the build-up of ice and other contaminants at insignificant levels.
• Upcoming meetings:
  • SCISAT-1 Commissioning Review, 27 February, Longueuil, Quebec
  • ACE Science Team Meeting, 19-21 April, Univ. of Waterloo, Ontario

January 30 to February 11, 2004

• Operations in this period have been entirely normal, with science commissioning activities completed for the FTS and nearing completion for MAESTRO.
• On 30 January Dr. Peter Bernath, ACE Mission Scientist, released some examples (H2O, HCl, NO2) of the first ACE atmospheric profile retrievals. He pointed out that refinements are yet to come regarding pointing knowledge (and therefore tangent height resolution), but even so could not resist noting "the retrievals look very good".
• There has been encouraging progress in the understanding of previously reported anomalies in attitude control behaviour, related to both magnetometer and startracker sensor outputs. It is expected the magnetometer fix (a bias adjustment) will be tested within a week or two, and the startracker fix is expected to follow thereafter. In the mean time, conservative operational procedures (which entail a higher degree of operational monitoring) are yielding entirely acceptable results.
• Between February 12 and April 7, the most Northerly measurements from SCISAT-1 will occur during sunset occultations. This should yield valuable data in connection with the buildup and, later, breakup of the Arctic ozone depletion.
• A SCISAT-1 Commissioning Review is planned for 27 February. This will mark the formal transition from commissioning to routine science operations.
• An ACE science team meeting is has been scheduled for 19-21 April at the University of Waterloo. One expects there will be a "buzz" of excitement with respect to the flight data received up to that time!

January 14 to January 30, 2004

This time period has been one of surprises:

• During a procedure to step the suntracker over its full range of motion, the suntracker interpreted the last step as a sign change (because of a 2's complement algorithm). This resulted in an on-going full-range motion of the suntracker that, after detection, was halted by ground command. A constraint on the max number of steps is now in place.
• During an intentional procedure to allow the satellite to drift through the eclipse portion of the orbit, the satellite pointing at the subsequent sunrise was ~5 deg off the center of the sun (vs. normal < 1 deg). Since the suntracker has a field of regard > 5 deg, it was not able to find the sun and this resulted in an on-going hunting motion of the suntracker. A constraint is now in place to prevent the suntracker from searching for the sun if the satellite pointing is not within an acceptable range.
• The startracker experienced another anomaly while enabled within the satellite control loop. This caused the satellite pointing to go sufficiently out of spec that the on-board computer commanded a transition to safe-hold mode. The recovery from safe hold required an uploading of optimum parameter values as determined by commissioning activities. In fact a particular table of values did not upload correctly, and this resulted in a second transition to safe-hold - the satellite safety system is working as designed!

Notwithstanding these surprises, excellent occultation science data has been acquired during the "normal" periods of commissioning activities. A sampling was distributed to ACE science team members (and others) on 23 Jan by Peter Bernath, Mission Scientist.

As of the time of writing, operations are back to normal and the science commissioning activities are again on track. These are expected to be completed within a week or so and, thereafter, routine science operations should become the norm.

A SCISAT-1 Commissioning Review is planned for 27 February. If successful, this will mark the formal transition from commissioning activities to routine science operations.

An ACE science team meeting is planned for mid-April (date tbc) at the University of Waterloo.

7 to 14 January, 2004

• As of 10 Jan, sunrise and sunset occultation measurements have been successfully acquired using both FTS and MAESTRO operating simultaneously. These data enable the characterization and optimization of a number of key science measurement parameters. This science characterization program is planned to continue until the end of January.
• Efforts are continuing to increase the automation of SCISAT-1 operations in order to maximize the delivery of flight science data.
• A plan of action has been developed to resolve the star tracker anomaly. A slight complication arises in that the execution of this plan conflicts, to some degree, with the maximization of acquired science data. However this conflict is being managed in full consultation with the ACE science team.

December 17, 2003 to January 7, 2004

• From December 17 to December 20, the first exo-atmospheric measurements using both FTS and MAESTRO were simultaneously performed. During these measurements, imager settings were fine-tuned and suntracker step size characterization was performed.
• During the holiday period - December 21 to January 7, only "good healthkeeping" commanding was performed.
• During 7-10 Jan, exo-atmospheric characterization of both instruments, operating simultaneously, will continue.
• Beginning Jan 10, sunrise and sunset occultation measurements using both instruments, operating simultaneously, will begin. This will enable the characterization of a number of science modes of operation and the further optimization of various instrument parameter settings.
• The startracker anomaly has not yet been resolved, although the matter did not receive much attention over the holiday period. Confidence remains high that the issue will be resolved in the near time frame.

10 to 17 December, 2003

• The simplified detector outgassing (decontamination) procedure was successfully tested this past week. The very good news is that this simplified procedure takes only approximately 15 minutes to accomplish full decontamination, and therefore does not present a conflict with the scheduling of priority science observations.
• System end-to-end commissioning for standard science operations has now begun. Over the next several days, routine-type science commands will be generated at the Science Operations Centre (SOC) and checked/uploaded by the Mission Operations Centre (MOC).
• The startracker anomaly has not yet been fully resolved. However the sensor continues to generate output data that is very helpful to the on-going analysis of the anomaly.
• This update service will recommence in early January.

3 to 10 December, 2003

• In order to minimize the effects of re-contamination of the cryogenically cooled FTS detectors, a simplified detector outgassing cycle has been developed based on the knowledge gained from previous decontamination cycles. This simplified cycle will be exercised on 11 December and, if successful, will allow routine decontamination cycles in the future with less intensive effort from ground operations personnel.
• FTS performance optimization and characterization is now nearly complete, and final commissioning activities on MAESTRO are scheduled for the week of 15 Dec.
• Attention is now being focused on system end-to-end commissioning for standard science operations. This entails verification of all communications and procedures between the Science Operations Centre (SOC) at the University of Waterloo, the Mission Operations Centre (MOC) at the CSA in Longueuil, and the spacecraft (S/C) itself. The intention is that the science team at the SOC will be able to generate a science command timeline per their desired observational priorities, and the MOC will be able to verify that the request does not violate system constraints (re system health and safety and/or availability of needed resources such as power and on-board storage). The MOC will then uplink the appropriate command sequences, receive the associated flight data, and notify the SOC of the availability of this data.
• As mentioned in a previous update, the startracker anomaly is now believed to be understood. A software fix has been uploaded to the startracker, and it is planned to test the fix on 12 Dec.

26 Nov-3 Dec, 2003

• The 2^nd FTS detector outgassing cycle was completed 28 November, and a comparison of "before" and "after" spectra clearly shows the effect of the contamination layer (mostly ice). In fact, spectra taken only 4 days after decontamination already indicate the beginnings of recontamination. This is not unexpected, and it is known that the rate of recontamination will decrease with the passage of time on-orbit.
• FTS performance optimization and characterization began on 1 Dec and will continue throughout the month. Simultaneously, additional commissioning activities will be performed on MAESTRO.

19 to 26 November, 2003

• The first ACE-FTS atmospheric spectra, computed from data generated during the suntracker commissioning activities, were distributed to members of the ACE science team by Dr. Peter Bernath (ACE Mission Scientist, University of Waterloo) on 20 November. His concluding sentence: "As you can see, they are of very high quality!"
• The suntracker commissioning was successfully completed on 21 November, with all performance parameters well within specified ranges.
• The 2nd FTS detector outgassing cycle has begun, and is expected to be completed by 28 November. Interferometric data was acquired just before the cycle was begun to see the "before" and "after" effects of the contamination layer (mostly ice).
• The star tracker anomaly, reported last week, has been analyzed and it is believed the (minor) issue has been uncovered. A correction is currently undergoing test on a ground simulator. If this checks out, the correction will be tested on-orbit.
• FTS performance optimization and characterization is scheduled to begin on 1 Dec. Simultaneously, additional commissioning activities will be performed on MAESTRO.

12 to 19 November, 2003

• A minor correction to last week's report on an ADCS (attitude determination and control) anomaly: as a result of the anomaly, the ADCS computer commanded the satellite out of science mode and into sun pointing mode (rather than into safe_hold mode). This indicates that the situation was substantially more benign than that implied by a command to safe_hold.
• The first atmospheric interferograms were acquired late on 18 November, as part of the suntracker commissioning activities. ACE Mission Scientist Dr. Peter Bernath (University of Waterloo) exclaimed surprise at the "super" quality of the data - especially given that the detectors are known to be contaminated by an ice layer and that the instrument has yet to be optimized for best science quality. Dr. Bernath hopes to distribute the initial processed results to the ACE science team on 19 November.
• The suntracker commissioning is expected to be completed on 21 November, after which it is planned to perform the 2nd FTS detector outgassing cycle. This will be followed throughout December by FTS performance optimization and characterization.
• An anomaly was detected last week when the output of the star tracker was fed into the satellite's control loop. First thoughts are that a parity (sign) issue is the cause, and further commissioning activity on the star tracker is being deferred pending investigation of the anomaly.

5 to 12 November, 2003

• A minor ADCS (attitude determination and control) anomaly occurred on 10 November while the satellite was over the South Atlantic Anomaly (SAA) and in the eclipse portion of its orbit. During eclipse the satellite relys on magnetometer sensor data for attitude knowledge, but over the SAA this data becomes more ambiguous than elsewhere in the orbit. As a consequence, the ADCS computer registered an "out of bounds" indication on pointing and commanded the satellite into safe_hold mode. Although being analyzed further, one solution may be simply to allow wider bounds on magnetometer sensor input errors during eclipses while over the SAA.
• Although a bit of time was lost as a result of the ADCS anomaly described above, the first occultation (i.e. with atmosphere) interferograms are expected to be acquired as part of the suntracker commissioning activities during the week of 17 Nov. In parallel, the satellite's star tracker will be commissioned.
• In the week of 24 November, it is planned to perform the 2nd FTS detector outgassing cycle. This will be followed throughout December by FTS performance optimization and characterization.

29 October to 5 November, 2003

• As planned, the "first light" exo-atmospheric interferograms were acquired from the FTS (Fourier Transform Spectrometer) on Thursday, 30 October. These were processed into spectrograms at the Science Operations Centre, located at the University of Waterloo. In his mail-out of first results to the ACE science team, Mission Scientist Dr. Peter Bernath exclaimed "We have an excellent FTS!"
• The "first light" exo-atmospheric spectra reveal the solar Mg emission line and the solar CO absorption lines, among many other features. Evidence is also present of the expected re-contamination of the detectors in the absorption bands associated with an ice layer. This ice layer is scheduled for removal during the 2nd detector decontamination cycle, scheduled to begin Nov 24.
• The first occultation (i.e. with atmosphere) interferograms are expected to be acquired as part of the suntracker commissioning activities beginning next week and continuing through the week of 17 Nov. During this same time period, as a parallel activity, the satellite's star tracker will be commissioned.
• FTS performance optimization and characterization will be done throughout December so as to be fully ready to acquire routine operational science data during the anticipated buildup of the Arctic ozone depletion, beginning in early January and reaching a peak in early March of 2004.

22 to 29 October, 2003

• The commissioning of the FTS (Fourier Transform Spectrometer) began this past week. Due to considerations regarding satellite operations, the first interferograms were taken while the satellite was on the night side of the orbit. As such these interferograms are associated with self-emission from the instrument, and they do indeed indicate proper functioning of the FTS. The sun-illuminated "first light" interferograms are expected to be acquired on Thursday, 30 October.
• From the interferometer data collected to date, the FTS development contractor ABB has established that the closed-loop speed stability of the FTS rotary arm is better than 0.05% RMS. This parameter is key to the excellence of science data quality, and is very good news indeed.
• "First light" spectral data has been acquired this past week from the MAESTRO instrument, and both the UV and visible channels appear to be functioning as expected. The formal commissioning of this instrument is scheduled for early December.
• The schedule for commissioning the suntracker has been accelerated to begin on 10 November. This activity is expected to generate quality science data, although the operational science data will not be acquired routinely until early January 2004.

15-22 October, 2003

• The commissioning of the science pointing modes of the ADCS (Attitude Determination and Control Subsystem) was completed successfully over the past week.
• The commissioning of the FTS (Fourier Transform Spectrometer) will begin on Thursday, 23 October, and "first light" interferograms are expected to be acquired on Monday, 27 October. This commissioning activity will continue through the full week of 27 October.
• The suntracker commissioning is scheduled to begin on 23 November, followed by instrument performance optimization and characterization throughout December. Although quality science data is expected to be acquired during these activities, the operational science data should be acquired routinely as of early January 2004.

8-15 October, 2003

• The commissioning of the science pointing modes of the ADCS (Attitude Determination and Control Subsystem) is taking place this week. This ensures, among other things, that the ADCS timing and pointing are correct for the full capture of occultation events and that a principal axis of the instrument field of view is aligned tangentially to the limb of the earth.
• The automatic reboot procedure for the MAESTRO instrument was successfully executed last week. The development of plans and procedures are on schedule for the completion of MAESTRO commissioning in November.
• The commissioning of the FTS (Fourier Transform Spectrometer) has been delayed by a week or so due to the need to finalize and validate the system-wide databases that ensure operational constraints are not violated. This precaution minimizes the risk of inadvertently compromising the health and safety of all flight systems. Accordingly, "first light" science data is now expected in the 4th week of October.
• The development of plans and procedures continues on schedule for the commissioning of the MOC-SOC (Mission Operations Centre - Science Operations Centre) data communications interface. The "first light" data volume will provide an initial opportunity to exercise this interface in a flight operational mode.

1-8 October, 2003

• The satellite is now under nominal roll control, which minimizes the view to the earth of the passive cryocooler. An immediate consequence of this is a dramatic cooling down of the FTS infrared detectors, now at approximately 78 degrees Kelvin - very close to that predicted by Ball Aerospace, the subcontractor to ABB for the cryocooler subsystem.
• The high-speed downlink data rate of 4 mbs (mega-bits/second) was successfully exercised during the past week. This data rate is essential for the complete downlinking of operational science data.
• The commissioning of the science pointing modes of the ADCS (Attitude Determination and Control Subsystem) will be done in the next week. This ensures, among other things, that a principal axis of the instrument field of view will be aligned tangentially to the limb of the earth.
• The plans and implementation procedures are progressing well for the commissioning of the FTS (Fourier Transform Spectrometer) interferometer and imager subsystems. This should yield "first light" science data by the 3rd week of October. Operational science data will have to wait the commissioning also of the instrument-mounted suntracker, scheduled for late October.

24 September - 1 October, 2003

• The spin-up of the satellite's momentum wheel to the nominal 2000 rpm (revolutions per minute) has been accomplished successfully. The associated fine control of the satellite roll rate, which minimizes the view to the earth of the passive cryocooler, will be completed by October 2.
• The high-speed downlink data rate of 4 mbs (mega-bits/second) will be exercised at all receiving ground stations during the next week. This data rate is essential for the complete downlinking of operational science data.
• Preparations are on schedule for the commissioning next week of the science pointing modes of the ADCS (Attitude Determination and Control Subsystem). This ensures, among other things, that a principal axis of the instrument field of view will be aligned tangentially to the limb of the earth.
• The plans and implementation procedures are progressing well for the commissioning of the FTS (Fourier Transform Spectrometer) interferometer and imager subsystems. This should yield "first light" science data by mid-October, although operational science data will have to await also the commissioning of the instrument-mounted suntracker.

17-24 September 2003

• The decontamination cycle for the FTS MCT and InSb detectors was successfully completed on 22 Sept.
• The crucial one-time pin-puller activity was successfully completed on September 20. ABB engineers, who developed the instrument, immediately observed interferometric fringes generated by the reference laser as a result of slight motions of the rotary arm -- confirming that the locking pin had indeed been pulled successfully.
• The spin-up of the satellite's momentum wheel, and the associated roll control function of the satellite's ADCS, are on schedule for completion by mid-next week.
• The schedule remains hopeful for "first light" instrument data in the first part of October.

10-17 September 2003

• The decontamination cycle for the FTS instrument's MCT and InSb detectors has been initiated, and will continue for a total of 5 days. The effectiveness of this decontamination cycle has already been confirmed by an increase in dc signal levels at both detectors.
• The crucial one-time pin-puller activity, i.e. the extraction of the locking pin that secured the FTS instrument's rotary arm during launch, will be performed on Saturday, September 20.
• The flight commands for the spin-up of the satellite's momentum wheel have been validated, and will be executed in coordination with the commissioning of the roll control function of the satellite's attitude determination and control subsystem (ADCS). Roll control is essential to the achievement of sub-100K temperatures at the MCT and InSb detectors of the FTS instrument.
• The schedule remains hopeful for "first light" data per the previous status update.

As of 9 September 2003

• The Launch and Early Orbit Phase (LEOP) of the mission was successfully completed within 2 days of launch. The satellite was successfully oriented so that the solar panel pointed toward the sun within a capture-control angle of 11 degrees. Early telemetry indicated that electric power generation and all temperature sensors were at nominal levels.
• An early concern was a slightly noisier command receiver than expected, although sufficiently minor that it has no impact on the communications function. A technical review of the receiver design, as well as flight data since launch, indicates that the source of the slight noisiness is benign and the level of it is not expected to increase with time.
• The power to the two scientific instruments has been switched on, and heaters for temperature control of the instruments are maintaining temperatures within operational limits The instruments remain in standby mode pending the completion of additional commissioning activities.
• The satellite fine pointing control has been successfully commissioned. This maintains pointing of the solar panel toward the center of the sun within an angle of approximately 1 degree. Finer pointing of the instrument look direction, to an accuracy of a few seconds of arc, will be accomplished with an instrument-mounted suntracker.
• It is anticipated that "first light" data from the instruments will become available as part of the instrument commissioning activities. If all continues nominally, this is expected by early October for the FTS and by late October for MAESTRO.