May 15th, 2007:
Constellation Status:
The THEMIS constellation continues to operate nominally and is in a very good state of health. All instruments are turned on and are collecting science data. All stored science and engineering data are recovered regularly with a success rate of nearly 100% across the constellation.
Recent Events:
Completed EFI deployment steps 0-12 on THEMIS C (see URL listed below). Please note that the deployment sequence was optimized and now only requires 14 steps (0-13). The only remaining step for this probe is the axial boom release (step 13) which is scheduled for later this week.
The EFI spin-plane boom deployment went very smooth - there were no issues with dynamic stability during the deployment or following spin-up maneuvers. The dual pulse spin-up procedure worked very well. According to the EFI team, the instrument generates science data with excellent quality.
Completed all required orbit maneuvers for the coast phase placement of THEMIS A, B and D.
May 14th, 2007:
Constellation Status:
The THEMIS constellation continues to operate nominally and is in a very good state of health. All instruments are turned on and are collecting science data.
Occasional hang-ups of the ETC FPGA that controls data acquisition from the SSTs and ESAs were observed again on multiple probes. The FPGA was successfully reset on these probes. A work-around is still tested on FlatSat. No other anomalies were encountered.
Recent Events:
Ran science-like orbits on all five probes.
Uploaded new IDPU FSW Version 0x43 (patch) to all five probes which fixes two issues (data compression and time tagging of FGM data). Data compression was successfully exercised on THEMIS D. FGM data are now time-tagged correctly on all five probes, improving attitude determination with MSASS significantly.
Started final EFI commissioning phase (steps 0-2) on THEMIS C (P2). On DOY 129 (March 9) the probe was spun up to 20 rpm, the EFI X and Y spin-plane boom doors were opened, and the X and Y axis booms were deployed by 5m each. The observed spin rate change during the deployment was nominal. The EFI Scientist reported nominal sensor operation.
Plans for Upcoming Weeks:
Continue with: EFI commissioning steps 3-15 on THEMIS C and orbit placement for the coast phase.
Deploy EFI booms on THEMIS D and E.
Test: data compression on probes THEMIS A, B, C and E; control of science data acquisition via instrument triggers.
Please refer to THEMIS Mission Operations Report No. 6 for additional reference material. Report No. 7 will cover DOY 113-127 (April 23 - May 7) and should be released by the end of this week.
May 2nd, 2007:
Constellation Status:
The THEMIS constellation continues to operate nominally and is in a very good state of health. All instruments are turned on and are collecting science data. No anomalies were encountered.
Events of Last Week:
Performed attitude precession maneuver to science north on THEMIS A-D, using axial thruster A2. All 20 thruster across the constellation have now been exercised and function nominally.
Performed spin-up maneuver to 20 rpm on THEMIS A and B, using the dual-pulse-per-spin thrusting technique with tangential thruster T1. This mode is required to be used for all spin-up maneuvers to maintain dynamic stability of the probes, once EFI spin-plane boom deployment has started.
Uploaded IDPU FSW patch 0x43, new IDPU script set 0004 and ETC Table Checker program to THEMIS C
Plans for Upcoming Weeks:
Per agreement, GSFC/FDF will reduce back-up orbit determination to one OD solution per probe per month on DOY 120 until the mission orbit placement begins in fall. UCB/FDC continues to generate OD solutions for all probes typically 2-3 times per week, and continues to deliver tracking data to FDF for each pass.
Upload IDPU FSW patch 0x43 to THEMIS D and E (DOY 120) Select ESA mode "Shocked Solar Wind" on THEMIS E
Upload IDPU FSW patch 0x43 to THEMIS A and B (DOY 123) Enable data compression on THEMIS D
Repeat FGM commissioning procedure on all probes near apogee (per request of FGM team)
Run science-like orbits on all probes
Perform perigee raise maneuver on THEMIS E (DOY 129)
Perform EFI deployement on THEMIS C over 6 orbits (DOY 129-136) Detailed plans will be finalized during the upcoming week.
Please refer to THEMIS Mission Operations Report No. 6 for additional reference material.
Report No. 7 will cover DOY 113-127 (April 23 - May 7).
March 29th-April 6th, 2007:
Current Constellation Status:
All five probes are safe and healthy, and are in stable orbits. The attitudes are nearly ecliptic normal. All science instruments are operational and are collecting data.
Please refer to the THEMIS Constellation Status web page for detailed, current status information (see below).
A preliminary orbit placement decision was made on March 27:
The mission orbit placement will begin in late August, and will be completed in preparation of the first winter observing season "Tail 1" when the probe orbits will be aligned with the Earth's magneto tail. Meanwhile, all five probes are maintained in temporary "coast phase" orbits.
Following the launch dispersion, the five probes ended up in nearly identical orbits where C is leading and E trailing the group D-B-A with differential orbital periods of -/+ 5 min, respectively:
<------C--------D-B-A--------E-----
The desired configuration for the coast phase is as follows:
<------B--------C-E-D--------A-----
Based on the probe placement decision, THEMIS C, D and E will have their EFI booms deployed early (see below), and should ideally be at the center of the coast phase constellation at apogee.
Recently Completed Tasks:
Performed perigee raise maneuvers with each probe to control the differential precession of the argument of perigee amongst the five probe orbits and to calibrate the thrusters:
DOY 87: THEMIS C perigee raise by 25 km to 585 km (delta V 1.3 m/s)
DOY 88: THEMIS A perigee raise by 70 km to 652 km (delta V 3.6 m/s) THEMIS D perigee raise by 70 km to 660 km (delta V 3.4 m/s) THEMIS E perigee raise by 70 km to 656 km (delta V 3.6 m/s)
DOY 93: THEMIS B perigee raise by 70 km to 691 km (delta V 3.6 m/s)
DOY 94: THEMIS C perigee raise by 70 km to 705 km (delta V 3.5 m/s)
Performed the first of a series of additional orbit maneuvers to position the five probes for the coast phase:
DOY 95: THEMIS D perigee raise by 363 km to 1050 km (delta V 20.9 m/s)
All delta V maneuvers were accomplished in side thrust mode, using the two tangential thrusters with a 60 deg thrust angle at a spin rate of approximately 20 rpm. Small attitude and spin rate changes were encountered as an undesired, but unavoidable byproduct of the side thrust maneuvers. These changes will be corrected later.
Performed post-maneuver operations, including maneuver reconstruction and calibration, orbit and attitude determination.
Refined mission trajectory design for the coast phase, based on inputs from the PI and the science team.
Completed various science-like orbits to test data acquisition modes.
Anomalies:
Two new anomalies were encountered during the report period:
IDPU Configuration Anomaly
On DOY 90 IDPU resets occurred on three probes (THEMIS A, B and D) when on-board science data compression was initiated out of an ATS load. The resets occurred on all three probes shortly after compression started. As a result, the IDPUs went into Safe Mode and turned all instruments off. The cause for the resets is under investigation and may be related to a configuration issue. Data compression had been tested extensively during TVAC and also on FlatSat with the FM6 (spare) instrument suite.
Instrument turn-on was postponed until the orbit maneuver on THEMIS B was completed on DOY 93. All three IDPUs were then commanded back into normal mode, and the instruments were turned back on. On THEMIS D the ESA HV and SSTs were purposely left powered off until after the orbit maneuver on DOY 95 to avoid damage to the sensors by thruster plumes. Turning these sensors off is required for each thrust maneuver.
BAU Packet Production Anomaly
On DOY 94 the THEMIS B BAU stopped generating housekeeping telemetry for those telemetry points that are read from the Power Control Module (PCM). These include most power and thermal telemetry points. Recovery operations began on DOY 95. Neither resets of the PCM FPGA nor a warm restart of the BAU restored the full telemetry generation. However, a cold restart of the BAU (without clearing the memory) succeeded and brought the spacecraft bus back into a fully operational state. The IDPU and instruments on this probe were turned on again on DOY 96.
Ongoing Activities:
All pass activities are conducted with FOT on console. Passes are currently still taken in blind acquisition mode, allowing a high degree of operational flexibility for re-planning.
ATS loads are used primarily to reconfigure instruments in various orbit regions and to support maneuver operations.
Characterization of instruments in science-like orbits. A dedicated 'fields' orbit for all five probes will start on DOY 98.
Telemetry recovery, archiving, processing and data trending.
Communications tests with BGS, using BPSK at the lowest six data rates to assess potential gains in link margin at large ranges.
Investigation of various anomalies.
Upcoming Tasks:
Maneuver operations for the coast phase orbit placement:
All probes will perform additional apogee and/or perigee change maneuvers over the course of the next few months to achieve and maintain the coast phase constellation. The maneuver sequence is designed such that minimum fuel is consumed and virtually all of the perigee and apogee changes count towards the mission orbit placement.
EFI boom deployment on 3 probes (THEMIS C, D and E):
THEMIS D (P3) will begin with the EFI boom deployment on DOY 106 (April 16). The entire sequence alternates between boom deployment steps, instrument test and calibration runs, and data recovery near perigee; this takes 6 orbits (8 days) to complete.
The EFI boom deployment sequences for THEMIS C (P2) and E (P4) will be interleaved and are currently scheduled to begin on DOY 128 (May 8).
Note that the EFI booms for THEMIS A (P5) and B (P1) will be deployed after their mission orbit placement is completed. These two probes require the largest fuel usage for their orbit placement. Delaying the boom deployment will allow for a rapid ascent of THEMIS B to the P1 orbit by using efficient attitude precession maneuvers and axial thruster burns for the delta V maneuvers. THEMIS A (P5) is the designated on-orbit spare and will have its EFI booms deployed, once THEMIS B (P1) has completed its orbit placement. The other three probes will perform their mission orbit placement using the tangential thrusters in "side thrust mode".
Operations Related Web Pages:
THEMIS Constellation Status:
http://soleil.ssl.berkeley.edu/ground_systems/themis_constellation_status.html
THEMIS Real-time Tracking Schedule:
http://soleil.ssl.berkeley.edu/ground_systems/themis_tracking_schedule.html
THEMIS Sequence of Events (complete mission pass schedule):
http://soleil.ssl.berkeley.edu/ground_systems/request_planning.themis.txt
Operations List Server:
http://www.ssl.berkeley.edu/mailman/listinfo/themis-operations
Please join almost 30 already signed up recipients on this list server to be sure not to miss any future email broadcasts related to THEMIS operations - it only takes a short moment to sign up.
March 14th, 2007: In the past day, we performed telecom tests at apogee with all probes and multiple ground stations. These were very successful showing us the probes can telemeter at 64 K bits per second to Berkeley throughout this orbit. Probe C and D SSTs were turned on again and left running in order to get a measurement with no ESA High Voltage sweeps. Probe E SST was reconfigured. Probe B ESA ions and electrons were brought up in High Voltage.
At the present time, ESA HV is running on A and B, while SST is up and running on C and D. Science data is being collected and returned successfully in Slow Survey mode. Assuming data looks good overnight, we'll raise ESA High Voltage on C, D and E while turning on SST A, B and E. That would complete the initial commissioning on all instruments.
March 12th, 2007: Today, ESA electron High Voltages were checked out on probes A, B, D and E. Each was ramped up successfully to full voltage and all four performed beautifully. Probe C ESA was not ramped up because of the ongoing set up issue with the ESA/SST controller. We plan to get back to that probe tomorrow.
March 11th, 2007: Today, the SST on Probe C was powered up again in order to check out the sun-blanking circuitry. Currents looked good and stable, but the expected packet telemetry was not coming through. Once again, SST was turned off while engineers worked on an updated plan for SST.
All probes are in good health and their orbits are well known.
March 10th, 2007: Today, ESA ion High Voltages were checked out on all five probes. Each was ramped up successfully to full voltage and all five performed perfectly. Probe A ESA was intentionally left at high voltage while the other probe ESAs were ramped down for the time being. The science team reports nominal performance from all five ESAs, and excellent science data quality from the THEMIS A Ion detector.
All probes are in good health and their orbits are well known
March 8th, 2007: Today, SSTs on Probes B and C were turned on and their attenuators were exercised. Probe D's SST was not commissioned since the SSR was still full from ESAs commissioning yesterday. Probe A and E SSTs were turned on, but due to sun in their apertures at these attitudes, their currents red-limited and they were turned off before the end of their contacts. By the end of the day, all SSTs were powered off in order to allow manevers to proceed.
Probes A, E, D and B were maneuvered to ecliptic normal, enabling better communications, stable power and thermal conditions. Fuel usage since launch has been a mere 0.2 kg.
Science and engineering data for all probes was played out. All probes remain in good health and their orbits are well known.
March 7th, 2007: Today, all ESA covers were successfully opened using their primary actuators. Each ESA was tested with its internal test pulser and all ESAs performed well. Later this week we will turn on the High Voltage to the ions and electrons.
March 5th, 2007: Today, we aborted planned maneuvers on Probes A, D and E due to poor link margin. The probes were over 87000 km range and could not sustain RF link to the BGS antenna. We are replanning these maneuvers for later in the week, while proceeding ahead with the commissioning in the current attitude.
All five probes remain in excellent health, with the Fluxgate, Search Coil, Electric Field and ESA Low Voltage on.
March 4th, 2007: Over the weekend, Probes B and C were maneuvered so that their antennae were north-south with respect to the ecliptic. While both maneuvers were successful in general, Probe B's maneuver on Saturday resulted in a side tilt of 40+ degrees to the ecliptic plane. This was confirmed when the Probe passed through perigee and its FGM data showed the tilt.
Probe C's maneuver sequence was modified to include newly determined information about the probes, so C's maneuver on Sunday was picture perfect.
Probes A, D and E will be maneuvered to ecliptic normal in the early morning of Mar 6 and, assuming those maneuvers go well, Probe B will be tipped up on Mar 7.
All five probes remain in excellent health, with the Fluxgate, Search Coil, Electric Field and ESA Low Voltage on.
February 27th, 2007: Today, Probes D and E were spun up to 20 RPM following their magnetometer boom deployments yesterday. All probes continue taking magnetic data in preparation for a maneuver to ecliptic normal attitude.
The planned maneuvers to ecliptic normal will be performed in steps, where Probes B & C will maneuver on Friday and Probes D, A & E will maneuver on Saturday. This allows science data to be recovered in an unusual mixed configuration; ie. two probes rotated with respect to the other three.
All five probes remain in excellent health, with the Fluxgate, Search Coil, Electric Field and ESA Low Voltage on.
February 26th, 2007: Today, Probes A, B and C were spun up to 20 RPM following their magnetometer boom deployments over the weekend. Probes D and E had their magnetometer booms deployed. All probes are taking magnetic data in preparation for a maneuver to ecliptic normal attitude at the end of the week.
All five probes remain in excellent health, with the Fluxgate, Search Coil, Electric Field and ESA Low Voltage on.
February 24th, 2007: The last 24 hours have seen an amazing amount of accomplishments on the five probes. All five EFI and SCM instruments were turned on, a calibration of Probe B FGM was performed, and all probes were spun down to 11 RPM. We recovered all engineering and science data from all probes, too.
As the probes have begun to separate a little, we were also able to contact three probes simultaneously using three different ground stations. Probes E, D and C telemetered to Berkeley, Santiago and Wallops at 512, 256 and 128 kbps, and the data routing network worked perfectly. Of the 20 passes during the day, Berkeley had 13, Santiago 1, Haartebeestok 1 and Wallops had 5 tracking passes.
All five probes remain in excellent health. Temperatures are very mild on the probes now in their nominal attitude with sun on their side panels.
February 23rd, 2007: Today, Probes C and B EFI and SCM instruments were turned on and Probe B FGM calibration performed at mid-range. All systems were nominal in current and temperature. The first THEMIS instrument data for EFI and SCM data were played out and looked nominal.
All five probes were de-spun from their initial spin rate of 16-17 RPM down to 11 RPM, in preparation for the upcoming magnetometer boom deployment. This involved firing the radial thrusters for 6 to 7.5 seconds depending upon the initial spin rate. As we expected, each spacecraft wobbled a bit, but telemetry and commanding were unaffected.
All five probes remain in excellent health. Temperatures are very mild on the probes now in their nominal attitude with sun on their side panels. Engineers are continuing data collection and analysis on two technical items. The first item involves the occasional false over-voltage trips in charging circuits and the second involves measuring the command and telemetry link performance. There were no over-voltage-trips today.
Communications with the probes have been very successful with Berkeley Ground Station but not yet with Wallops. Last night we had successful telemetry at 64 KHz at a distance of over 70000 km using Probe B yet we were unable to lock on RF carrier with Wallops just moments earlier.
February 22, 2007: Today, on all Probes the Instrument Data Processors, FluxGate Magnetometers and ESA Low Voltage Power Supplies were turned on and checked out. All systems were nominal in current and temperature. FGM sensor data recording began and we should see the first science data play out in the next orbit.
Probe A was rolled so that the sun is on its side-panels rather than on its top. This will cool the top down.
All five probes are in very good health. Temperatures are very mild on the probes now in their nominal attitude with sun on their side panels. Engineers are finalizing data collection and analysis on two technical items at this time. The first item involved the occasional false over-voltage trips in charging circuits and the second involved measuring the command and telemetry link performance.
Communications with the probes have improved greatly due to better orbit and attitude information. For example, last night we had successful telemetry at 64 KHz at a distance of over 50000 km using Probe A
February 21st, 2007: Today, THEMIS Probes B, C, D and E were successfully maneuvered 33 degrees as planned to have sun on their side solar arrays. Each maneuver took about 2.5 minutes while each probe fired 40 pulses on one of the axial thrusters in phase with the spin. This attitude provides better temperatures around the probes as well as better communication to the ground. By plan, Probe A was left in the launch attitude for one half orbit until we contact it one more time with TDRS. After that time, Probe A will be rolled to the same attitude as the other four.
All five probes are in very good health, but the team is currently working two technical items at this time, one regarding occasional false over-voltage trips in charging circuits and the second involves measuring the command and telemetry link performance.
First, the occasional false over-voltage-protection trips are essentially due to the fact that the the batteries are fully charged. Small noise on the battery readings have caused the circuits to occasionally think that the battery is too full. In response, the circuits shunt power for a few minutes until the battery voltage is a fraction lower. It has become apparent that the solar arrays are putting out more power than projected, and that the shunts are barely able to regulate. Thus, we have turned on additional heaters to balance the energy in the probe.
Second, initial poor communications with the probes is to a large extent due to a shorter than predicted orbit. The orbits are now 1.073 x 14.697 Re at 15.9 degrees. As we have learned how to point the antenna better, communications at high data rates are a regular occurrence. Still, we've noticed that Charlie and Bravo have the best performance while the other three have 2-5 dB dips in their signals at certain orientations. These dips may be due to the un-deployed magnetometer booms on the top of the spacecraft and may go away when we deploy them Sunday 2/25/07.
February 17th, 2007: NASA's THEMIS mission successfully launched at 6:01 p.m. EST from Pad 17-B at Cape Canaveral Air Force Station, Florida. All trajectories appeared right on target. First contact at the Berkeley Ground Station was successful.
January 29th, 2007: Today the THEMIS spacecraft will be mated to the 3rd stage of the rocket. You can get video of this by clicking on the link "AE Video 1 Streaming Feed" at the following URL: http://countdown.ksc.nasa.gov/elv/.
January 26th, 2007: THEMIS will be launched from the same Pad as STEREO. Jetty Park is 2.9 miles from the pad and is apparently closer than the official site. Visit this website for information about launch viewing: Where & How to Watch Delta 2 Launches.
January 24th, 2007: THEMIS passed its Mission Readiness Board review yesterday. The NASA Associate Administrator for the Science Mission Directorate, Mary Cleave, stated that the mission is a pathfinder for future Heliospheric constellations and thanked the team for its efforts in making it possible for the entire community. Deputy AA Colleen Hartman stated that this is a scientifically very exciting mission and that she felt really fortunate to see it through end-to-end in her term. Dick Fisher, Heliophysics Division director, stated that the team performance in general and in this review in particular, sets a very high standard for missions to come.
"Multipoint observations of the magnetosphere and its coupling to the ionosphere and the solar wind"
The Science Meeting before THEMIS Launch, will be held at the Radisson Resort at the Port in Cape Canaveral, Florida from February 13-14, 2007.
