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MISSION STATUS ARCHIVES:
Spacecraft, Instrument and Science Processing System
04-25-07 to 02.07.08

AIM Spacecraft Bus Status

Electrical Power System

The Electrical Power System (EPS) is operating nominally, providing adequate power with healthy margins. No issues have occurred with switches or shunt control.

Solar Array

The solar array deployment was nominal. The array is providing approximately 23.5 Amps of peak current as measured by the on-board current sensor. The received power provides healthy margins for an extended mission. Full battery recharge is achieved 23-25 minutes into the 61 minute sunlight portion of the orbit. This illustrates more than enough margin such that solar array degradation will not be a life-limiting factor.

Battery

Typical eclipse minimum state of charge is 73-76 %, and typical peak state of charge is 97 %. This is within the expected pre-launch range. Battery temperature is being maintained between -4 C and +4 C, depending on location within the battery. With these conditions, the battery will easily support the mission for at least 5 years and more.

Attitude Control System

The Attitude Control System (ACS) performance is excellent and meeting all pointing and knowledge requirements. Some ACS software parameters were adjusted post-launch. In addition to the expected updates for commissioning, the following updates occurred: Contingency Mode parameters were updated to point the solar arrays 30 degrees off of the sun in order to reduce the array temperatures in this mode; ACS tables were updated on May 2 and the Star Tracker RAM was patched on May 4 to prevent loss of track with the Moon in the Star Tracker field of view; and some related ACS table parameters were also subsequently updated. Momentum dumping was disabled during Sun-Target mode on June 21 in order to provide more stable pointing during SOFIE observations. The last update occurred on June 28, 2007, which adjusted the gyro-Star Tracker on-board alignment matrices.

No degradation or unexpected performance is being experienced in the ACS. The only potential life limiting items are the reaction wheels; however, the wheel control software is designed to minimize zero crossings and will enable lifetime well beyond 5 years.

Thermal Subsystem

The Thermal Subsystem is operating nominally and has not shown any sign of degradation. All heaters are functioning normally. Bus temperatures have been very stable since the last thermally-significant operation on June 5, 2007 (lowering the TCVR heater set points). There has been a slight up-trend of ~ 3° C between the summer solstice and early November, which was expected due to the decreasing Sun distance over this period.

Temperatures are running slightly warmer than per pre-launch plans, in particular at the TCVR and RW-Z. This is due to the operational choice to leave the heaters for these two components at higher set points than per the pre-launch plan, in an attempt to prevent aggravation of the receiver subcarrier lock issue. However, while the temperature has been higher on the TCVR, there has been essentially no cycling of temperature (< 2° C variation over the orbit). Temperatures should not be a life limiting factor.

Command & Data Handling Subsystem

The Command & Data Handling (C&DH) subsystem has been performing nominally. No significant C&DH issues have been noted. The mission performs occasional dumps of the EEPROM contents in the APE and Uplink cards (which do not have their own scrubbing), and there have been no EEPROM integrity issues. On-board clock speed was calibrated after launch, and is currently showing a drift of approximately 0.3 msec per day. Even without further adjustment, if this drift rate holds, the clock will be sufficient for bus activities for at least 10 years. On-board memory scrub routines have encountered occasional single-bit errors in the mass memory, which have often correlated to the South Atlantic Anomaly. This is an expected artifact of the radiation environment, and the Triple Modular Redundancy (TMR) of the memory is handling these cases as intended.

Flight Software

The Flight Software (FSW) has been operating nominally. CPU usage has been 38% on average, and maximum 55%. To date, two patches to OBC RAM have been made on-orbit (OBC 6.3 and OBC 6.4), and both have gone smoothly.

RF downlink

Transmitter performance has been nominal, with no issues noted since launch. The pre-launch plan was to leave the transmitter off nominally, and only turn it on during GN/high rate passes. Also, it was not planned to operate in TDRSS/low rate mode except during exceptional circumstances. In contrast, actual usage has been to leave the transmitter on continuously, and to regularly return to TDRSS/low rate mode after every high rate pass. This is being done so as to minimize temperature variations in the receiver and to provide for maximum downlink coverage.

RF uplink

The RF receiver has exhibited a significant anomaly in which it sometimes will not lock onto the uplink subcarrier signal. Approximately 3 ground network passes plus 7-10 TDRSS passes are typically attempted per day, which allows for significant statistical data to be collected on the receiver performance. The percentage of successful uplink contacts per day is plotted in Figure 5.1.7-1 from launch through early January.

The pattern exhibits a general condition of about ~20% of total uplink possibility. It is not known whether recent performance is a reliable indicator of future performance. Other than the intermittent ability to achieve subcarrier lock, the receiver and all of its telemetry have been normal.

In order to maximize mission success in light of this receiver anomaly, the following changes on the spacecraft bus have been made:

• On-board command storage has been increased from 6 days to 24 days. This provides the ability to seamlessly collect science data while experiencing an uplink outage of up to 20+ days. To date, the longest period without uplink capability has been ~ 6 days.

• Bus flight software updates have been made which allow for science collection in the event that no further commands are received by the spacecraft. These updates include:
- an autonomous state vector update routine which uses eclipse entry timing plus on-board static table data to achieve the required on-board orbit knowledge,
- a simplified on-board ACS pointing sequence to continue SOFIE and CIPS data collection, and
- automatic data dumping upon detection of uplink carrier.
Additionally, CIPS and SOFIE sequences are on board to control their science data collection in the event of no further commanding. In this scenario, CIPS and SOFIE will continue to collect data, but there will be increasingly long periods in which the common volume is not imaged by CIPS due to the simplified ACS pointing sequence.

• On-board mission planning software has been uploaded, which will provide reliable pointing of CIPS at the common volume. This effectively removes the limitations due to spacecraft pointing and significantly increases the probability of adequate orbit knowledge so that all common volume science data will can continue to be returned in the case of an extended uplink outage.

The following bus changes are in development. Once loaded, these updates will further increase the science collection capability and mission robustness if the receiver were to no longer accept uplink:

• Implementing on-board sequences in response to ground-controlled RF ‘signaling’ patterns (a.k.a. Morse code commanding), without relying on subcarrier lock. This will provide great robustness as it will allow the ground to command resets and recovery from transient anomalies. There is also the opportunity for signaling changes in autonomous mission parameters, which would allow for even further mission longevity in the absence of subcarrier lock. This capability is currently in development and is planned to be tested and uploaded to the spacecraft prior to the 2008 northern hemisphere season.
The final stages of achieving spacecraft autonomy are nearly complete and all software changes to do this have been uploaded. In this condition, the mission can go on indefinitely with no commanding. The only exception will be in the case of a spacecraft safehold contingency situation, in which case, command capability will be very important in order to diagnose and fix any anomaly. The spacecraft autonomy capability has been tested in a passive mode in orbit and after the current southern hemisphere season is over, it will be tested actively, implemented and made operative for the 2008 northern hemisphere season. With the addition of Morse code commanding prior to the 2008 northern hemisphere season, the spacecraft will be even more robust due to commandability even in the event of no uplink subcarrier lock. Consequently, the AIM spacecraft is robust and will be capable of supporting an extended mission and many more science seasons.
Software sequences have been put on board such that if science data is no longer being collected (e.g. due to a new anomaly) and there has been no uplink for an extended period, then the spacecraft will perform various actions to attempt to return the receiver to a functioning state. These actions include, among other things, increasingly-wide temperature cycles on the receiver, and cycling various electronics boxes. This ensures that every possible attempt is made to regain command capability should it become necessary.

AIM Instrument Status

SOFIE

SOFIE has been performing very well on orbit, providing 15 sunset measurements each day at latitudes from 65° - 85°S and 15 sunrise measurements each day at latitudes from 65° - 85°N. All products, except CO2 and NO, are now being produced routinely and are already at a scientific high quality. The CO2 retrievals require that the two CO2 channels (4.3 microns and 2.7 microns) be inter-calibrated to very high accuracy, which requires lengthy in-orbit tests and calibration. The NO measurements are delayed due to an unexpected sensitivity to detector temperature. An ongoing development effort is underway to produce accurate corrections using detector temperature measurements and in-orbit characterization of detector heating behavior.

SOFIE is performing at pointing, noise, and drift levels necessary to achieve all measurement objectives, meeting or exceeding all pre-launch requirements. On-orbit pointing stability is typically 2-3 arcseconds during science measurements, easily meeting requirements. The knowledge requirement for FOV position on the solar image of < 1 arcsecond is determined by the SOFIE sun sensor array (SSA) which is co-aligned with the FOV. The measured solar image is currently tracking the solar edges on the SSA to a precision of better than 0.2 arcseconds, again easily meeting the requirement. Post processing is expected to eventually reduce this even further to under 0.05 arcseconds.

SOFIE autonomy for prediction and execution of its own science events is on-board and functioning nominally. The ability to seed the SOFIE autonomy in the absence of receiver bitlock has been added as part of the overall system robustness effort. With this added autonomy and robustness, the SOFIE instrument is well suited to an extended AIM mission.

CIPS

The CIPS instrument has performed flawlessly on-orbit. The instrument is expected to continue operating well into an extended mission as it currently shows no signs of performance degradation.

CIPS is also well-suited for AIM autonomous operations. CIPS has the ability to store internal instrument sequences for both CIPS and CDE operations. This allows mission operators to have a full month of operations loaded on CIPS in case of delayed uplink communications. In addition, if communications are lost for a longer period of time, CIPS will begin autonomous operations which will allow it to continue taking science data indefinitely, performing nominal science observations based on orbit events (eclipse exit and entry). CIPS autonomy also includes detection of the PMC science season (northern vs southern hemisphere), allowing the instrument to take images over the correct pole. Work is underway as part of the mission autonomy efforts to ensure that the onboard sequences are not lost should the instrument lose power. This will allow for immediate beginning of CIPS and CDE science collection upon repowering of the instruments, rather than to have to wait for the sequences to be reloaded during available uplinks.
CIPS’s ability to take images of the common volume has been preserved as part of the autonomy efforts such that the s/c rolls as necessary to place the common volume in the CIPS FOV utilizing beta angle prediction.

CDE

The CDE instrument continues to operate with nominal housekeeping signatures. CDE has two performance issues that are being successfully mitigated. First, the instrument registers more science events than expected. CDE self-monitors science activities and has 'autonomy' rules to change thresholds or pause science collection on an individual channel to regulate downlink volume. These parameters have been modified and are currently reset daily to assure optimal performance. This is currently done via the spacecraft ATS. If the ATS expires, the CIPS sequence will take over this daily maintenance. Second, the instrument periodically 'watchdogs' after detecting a stray 1 pps signal or overflowing a tier during processing. This does not affect the performance of the instrument, but if the count were to reach ten watchdogs without a reset, the Flash memory would be turned off and some data collection parameters would revert to pre-flight modified values, decreasing the science data return. In order to mitigate the issue, if the watchdog count changes the instrument is reset to clear the count in an automated process via a TMON.
Like CIPS, CDE is also well-suited for AIM autonomous operations. CDE does not require commanding aside from the mitigations described above. The monthly calibration activity is currently done manually, but will become autonomous if CIPS falls into its autonomy mode.

AIM Mission Operations Center Status

AIM was launched successfully on April 25, 2007 into a near-circular, 600 km sun-synchronous orbit at 97.79º inclination. Over the next 37 days, a series of tests verified the on-orbit performance of the satellite and instruments. A significant problem with the receiver was encountered in which it often does not achieve lock on the uplink/forward link sub-carrier, thereby preventing any commanding activities from the ground. Ground initiated commanding, and the loading of stored commands has been limited to those contacts where “bit-lock” is achieved, and additional SN support is now used to mitigate this problem (also see the Spacecraft Bus Status section). Instrument commissioning was completed without further incidence and science operations commenced in early June, 2007. Several flight software and table modifications have been implemented to improve the robustness of the system and its ability to collect science data with limited uplink opportunities (see the AIM Spacecraft Bus Status section for details).

Current predictions indicate that AIM will stay above its end-of-life orbit altitude of 450 KM until ~2017. Predictions show that beta angle does not begin to exceed +/- 9° until ~2011, thus ensuring full common volume science through at least that time period. Beyond that timeframe, each instrument can continue to perform valuable science independently.

Three GN contacts and three SN events with AIM are scheduled per day to facilitate the uplink of new command sequences and the downlink of recorded telemetry. In addition, eight to ten additional SN events are scheduled overnight to accumulate bitlock statistics. Originally, three GN contacts per day during PMC Season and five per week the rest of the year were planned.

Standard NASA services are used to connect the MOC to the primary ground stations located at Svalbard, Norway, Poker Flats, Alaska and Wallops Flight Facility in Virginia, as well as to the SN ground terminals at White Sands, New Mexico. In the time since launch, an additional aperture at Poker Flats, Alaska has been certified and certification of an additional aperture at Svalbard, Norway is in progress. This added diversity significantly increases the reliability of the AIM ground network.

For AIM, the FOT is responsible for planning and scheduling the observatory activities each day to support the collection of science data. Besides planning, the FOT conducts real-time operations and post pass analysis of the housekeeping data from the satellite bus and the instruments. Plots are posted to the website after every contact for FC review, and plots are checked daily. The Level 0 data products are made available to the SOFIE POC, and Level 1 data products are then made available to the CIPS and CDE scientists and engineers for the generation of higher level data products. Routine science processing activities run unattended, with personnel regularly monitoring data processing activities and data quality. Over 99% of the data collected on board has been successfully captured on the ground and delivered to the science team.

To support the extended mission, a few updates to the AIM ground system will be needed which would include, for instance, increased disk-space.

AIM Science Data Center Status

SOFIE Science Data Center

The SOFIE Science Data Center is now fully operational with Level 0 through Level 2 data being produced on a routine basis and recorded in the SOFIE database. SOFIE is collecting 30 occultation events each day, and processing of these events is being carried out at the Science Data Center. The collection rate (fractional amount of data collected vs. data potentially available) of for data since May 2007 is 99%.

Verification and validation of the SOFIE data is underway. Once the validation is completed, data metafiles will be provided to the Project Data Center at Hampton University. All Level 2 data will also be available through the SOFIE Science Data Center at GATS.
The data access and management software on the SOFIE web site is in place and ready for production processing, and currently provides quick-look plots and ASCII data files on an event-by-event basis. Software is in place to automatically generate NetCDF science data product files. The process for routinely producing these data product files has been tested, and will commence upon authorization of the instrument and mission PIs. Current data processing and storage resource requirements are within the project estimates and readily handled by the GATS computing infrastructure.

CIPS Science Data Center

The CIPS Science Data Center is fully operational and all planned data products are being produced by the system in a routine fashion. Our Level-4 analysis product, Cloud Properties, identifies cloud albedo and particle sizes, as planned.

The biggest challenge for the CIPS Science Data Center has been the receiver bitlock issue and resulting changes in the mission and instrument operation approach. In this operations mode, CIPS continues to send data to the ground between cloud seasons, which has increased our needs for data storage beyond what was originally expected. This has resulted in twice the planned amount of data to process, manage, and archive. Since the system was originally scaled to support a two-year mission, we will continue to be able to absorb these needs through the first year of operations. After the first year of operations, the CIPS Science Data Center will require modest additional funding for storage and data management.

CIPS data products are currently being archived at the CIPS Science Data Center at LASP and will be made available to the public beginning in February 2008 via the AIM Project Data Center at Hampton University. All interfaces for CIPS and CDE data have been tested and associated data products are ready for delivery.

To support the proposed plan for an extended AIM mission, the CIPS Science Data Center will require one FTE to manage calibration updates, software updates, reprocessing, data distribution, and continued archival activities. Additionally, one-half FTE will be needed for algorithm development to support new products that would provide insight into global ozone density and gravity wave characteristics. We will also need to purchase additional computer hardware to accommodate the increased needs for data storage.

CDE Science Data Center

Preparation of CDE data products has been challenged by elevated noise in the raw CDE data. Data products are being regularly produced by the science processing software, but the higher-level products need additional work to characterize and remove the noise before those products will be scientifically usable. This effort is the current focus of the CDE team and is expected to be completed before the start of the extended mission. For the extended mission, one full-time graduate student is required in order to maintain calibration updates, processing, and data archiving activities.

Project Data Center


The AIM Project Data Center hosts the AIM website, serves as the public interface for finding and retrieving data from the instrument data centers, and acts as host for the common volume data. The basic operational capacity for each is in place and operational. Ongoing development is currently proceeding to increase the ease with which the public can access the AIM data.

The AIM website, http://aim.hamptonu.edu, is fully operational and contains general information about AIM, updated news releases, links to more in depth information on the design and performance of the
spacecraft and instrument. Information about AIM's orbit is available along with a web based tool for predicting ground overpasses. A form to receive automated weekly predictions of overpasses is available to the public.

The Project Data Center is receiving meta-data from the instrument Data Centers and is making this data available to the public. The user interface to access the data is functional, but work on improving the usability is continuing. Work to integrate the AIM data search with the Virtual ITM Observatory (VITMO) will begin shortly.

The common volume data is created from the overlapping subset of the CIPS and SOFIE data products. Software for creating the necessary subsets has been developed. Production and availability of the common volume data will begin shortly.

Mission Status Archive

Spacecraft & Instrument Status

2017
2017.03.01
2017.01.26

2016
2016.11.28
2016.08.19
2016.07.29
2016.05.26
2016.04.19
2016.03.08

2015
2015.07.28
2015.06.20
2015.05.16
2015.04.30
2015.03.09

2014
2014.11.17
2014.10.31
2014.10.13
2014.09.25
2014.08.14
2014.06.01
2014.05.03

2013
2013.10.29
2013.05.31

2012
2012.12.10
2012.10.24
2012.09.12
2012.07.20
2012.04.26
2012.02.10

2011
2011.09.24
2011.06.01
2011.05.08
2011.02.15

2010
2010.12.03
2010.11.05
2010.10.01
2010.09.10
2010.08.10
2010.07.01
2010.06.07
2010.04.25
2010.03.18
2010.01.22

2009
2009.11.13
2009.10.13
2009.09.12
2009.08.08
2009.07.17
2009.06.25
2009.05.01
2009.04.03
2009.03.16
2009.03.01
2009.02.10
2009.01.19

2008
2008.12.22
2008.12.05
2008.11.01
2008.10.01
2008.09.03
2008.08.15
2008.08.01
2008.07.11
2008.07.04
2008.06.27
2008.06.20
2008.06.13
2008.06.06
2008.05.30
2008.05.23
2008.05.16
2008.05.09
2008.05.02
2008.04.25
2008.04.18
2008.04.11
2008.04.04
2008.03.28
2008.03.21
2008.03.14
2008.02.07
2008.02.07
2008.02.07

04-25-07 - 02.07.08

Summary Status

Science Status

Spacecraft, Instrument and Science Processing System

 
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Responsible Official: James M. Russell III

Web Curator: Emily M. W. Hill
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