10/2011: 2nd Demeter International Symposium
During the second Demeter International Symposium that took place at CNES headquarters on October 2011, from 10th to 12th, 80 geophysicists from all over the world met to present new results obtained from the vast quantity of data acquired during the six and a half years mission of this satellite.
Read the complete Press Release on CNES website (in French).
03/2011: Successful disposal of Demeter
To limit the number of debris growth around the Earth, most of the space agencies have adopted near 2000 rules implementing good practices for disposal of satellites. Coming into force at the end of 2010, the French Law on Space Operations, together with the associated Technical Regulation prepared by CNES, gave a mandatory aspect to these rules (tank passivation, electric passivation, re-entry within less than 25 years for the low orbits).
Demeter was the first satellite of the Myriade family designed with a low cost approach. The propulsion system was using hydrazine stored in a bladder tank and the gauging system was presenting significant uncertainties. When preparing the retirement operation, the main concern was when will occur the final depletion and what will be the behavior of hydrazine. This last point was considered as a technological experiment with an extensive analysis of the process to define a strategy avoiding any risk of tank explosion. Indeed, as the rationale for propellant depletion is to prevent break-up or further generation of orbital debris, the implementation should not result to an explosion. Finally a safe strategy was made available to the operational team and the tank passivation was performed beginning of 2011.
Demeter tank passivation operations were consisting in a series of semi major axis manoeuvres to empty gradually the tank while keeping control of the satellite.
During each manoeuvre, the variation of the semi major axis commanded was ±1.6 km corresponding to 2 minutes burn, which enables to avoid any risk of auto-explosion of the hydrazine. One should note that, in this case, there was no requirement for large reduction of Demeter orbit semi major axis because on one hand the estimated duration of the entry in the atmosphere was still lower than 25 years on the operational orbit, and on the other hand the lower reachable orbits were in potential conflict with other satellites.
In total, 15 manoeuvres have been realized, Demeter orbit have been lowered by 1.4 km.
The loss of efficiency of the propulsion system has been reached during the 13th manoeuvre, then two additional manoeuvres have been realized to observe the system behaviour during low hydrazine pressure burn.
The satellite was declared non manoeuvring at the end of tank passivation operations, which lasted 5 weeks.
By design, a satellite is extremely robust to any event that could lead to its loss. Particularly, the sub-systems are able to restart automatically and it is impossible to definitively cut off the power supply from the ground. The bypass strategy was to orient the solar panel in a direction opposed to the Sun until the batteries were completely discharged. But, without attitude control, the solar panel could eventually be oriented towards the Sun and recharge the battery, which could result in an automatic restart of the computer and a switch on of the satellite equipments (notably the on board emitters). To avoid this situation, a flight software, only composed of inoperative code, was uploaded with the last command.
The electric passivation operations took place on March 17, 2011, date of the upload of the last commands, which was performed with a lot of emotion, in presence of the operational team as well as the project development team.
The end of a chapiter... Demeter, as first satellite of the Myriade family, demonstrated magnificently the capabilities to offer innovative missions at low cost and to comply with debris mitigation rules.
The satellite turned off on March 17 at 17:37:45 in direct visibility of Kiruna, after more than 5 years of good and faithful services for an initial planned lifetime of two years.
12/2010: Demeter last scientific commands
The final science commands established by the science ground segment at LPC2E (Chemistry and Physics of the Environment and Space Laboratory) was recieved on board Demeter at 9:03 on 7/12/2010. This command brought to a conclusion Demeter's Science Mission on the 9/12/2010. This was an emotional moment for all of the CNES team.
The Demeter mission, the first Myriade microsat developped and launched by the CNES, leaves us a rich heritage of six years of data which have allowed scientists to significantly improve our knowledge of the ionosphere and to think up new experiments sur as the Taranis mission. This data will continue to be used in studying the link between ionospheric perturbations and seismic and volcanic activity.
The final satellite operations will begin shortly, including a procedure to burn-up remaining fuel on board and passivation of the satellite.
01/2010: Demeter was above HAITI 3 days before the earthquake
Observation performed by Demeter 3 days before the Haiti earthquake (magnitude 7) which occurs on January 12, 2010 at 21.53.09 UT (epicentre located at 18.451°N, 72.445°W). The top panel shows the variation of the electron density recorded at the satellite altitude during night time. The red triangle in the bottom panel indicates the time when the satellite is just above the future epicentre. A decrease of the density is locally observed around this area.
10/2009: A remarkable event registered by Demeter before the Samoa earthquake
Demeter observations 7 days prior to the M8 Samoa Earthquake which occurred on September 29, 2009 at 17.48.11 UT (location 15.51°S, 187.97°E). From the top to the bottom, the panels show the electron density, the electron temperature, the O+ ion density, and the earthquake occurrences along the satellite orbit. The red triangles indicates the closest approach to the Samoa earthquake and the many aftershocks. It can be observed an increase in the densities and a decrease in the temperature which are well localized above the future epicenter.
04/2009: Press release concerning the GRL paper by Fullekrug et al. (2009)
03/26/2009: Demeter Exploitation Review at CNES Toulouse
27-28/03/2008: Demeter Exploitation Review at CNES Toulouse
03/29/2007: New version of the platform flight software correcting the datation anomaly of one second
03/19/2007: Demeter registers perturbations in the ionosphere
Influence of VLF (Very Low Frequency) transmittters on the ionosphere
NWC in Australia is a very powerful transmitter of the US army (1000 kW) which sends waves at 19.8 kHz. The figure shows the perturbations induced in the ionosphere by this transmitter around 14.52.30 UT. These perturbations are registered when Demeter is close. The top panel represents a spectrogram in the HF (High Frequency) range where we can observe a characteristic frequency of the plasma which is excited around 1.8 MHz. The following panel shows a VLF (Very Low Frequency) spectrogram of an electric component with a dramatic increase of the signal over all the frequency range (the transmitter frequency can be observed at 19.8 kHz). Then the electronic density and temperature measured by the Langmuir probe are plotted. The curves indicate a large variation of these ionospheric parameters as in the bottom panel which shows the ion temperature measured by the plasma analyzer. During two years more than fifty typical events as this one have been registered and the orbit projections at the time of the perturbations have been plotted on the following map.
The star indicates the transmitter position in the North-West of Australia and the square indicates the geomagnetic position of this transmitter at the Demeter altitude (700 km). One can see that these perturbations are centred at 700 km around the magnetic field line whose foot corresponds to the ground position of the transmitter. This ionospheric heating covers an area of about 500000 km².
18/01/2007: Second Demeter Exploitation Review
07/07/2006: Decision to extend by another 2 years the scientific mission, which will thus continu until summer 2008
06/14-06/16/2006: International Symposium Demeter in Toulouse
For more information, please consult the symposium web site at:
12/05/2005: Orbit lowered to 660 kilometers, the orbit phasing is nearly unchanged
03/31/2005: The data acquired by Demeter augurs interesting scientific results
The ionospheric data recorded by Demeter since the beginning of the mission are of high quality, and important events have been already registered. The following figures give a good idea of the Demeter possibilities. They are related to the main scientific objectives of Demeter:
- the survey of the Earth electromagnetic environment,
- the emissions linked to the anthropogenic activities,
- the ionospheric perturbations linked to the seismic activity. The main purpose of the project is to perform a statistical analysis with many events in order to determine the main characteristics of the seismo-electromagnetic effects. It is too early to perform such statistics but data recorded during selected events are useful to determine the sensitive parameters which must be particularly surveyed in this statistical analysis.
Electromagnetic waves recorded by Demeter on November 10, 2004 during the most important magnetic storm of the year (Dst= -400 nT). The top panel shows a spectrogram of the electric field and the bottom a spectrogram of the magnetic field in the ELF range. The intensity of the emissions is colour-coded according to the scale on the right. The data correspond to a complete half-orbit. On each side we observe at high latitudes, intense emissions of "hiss". All along the orbit the "hiss" emissions have a cutoff frequency which corresponds to the proton gyrofrequency. In the middle, quasi-periodic emissions with a funnel shape are observed around the magnetic equator.
Spectrogram of an electric component recorded by Demeter on July 23, 2004 during the commissioning phase (this explains the vertical white lines which correspond to changes of mode). The geophysical parameters are plotted under the panel. There are 11 minutes of data. A set of lines are observed (they are not interferences) whose central frequencies are separated by ~ 50 Hz. These horizontal lines are limited by the cutoff frequency of the natural waves (proton gyrofrequency). They suffer an important growth close to the magnetic equator which is the favoured zone for wave-particle interactions. These lines are not at the exact harmonics of the 50 Hz. They are called MLR (Magnetospheric Line Radiation) and are supposed to be due to radiation emitted by the power lines.
10/05/2004: Demeter register near-periodical waves which extension was unknown
The possibility to register the data with a large resolution all along the orbit allows to reveal natural emissions which extension was not known. For example, Demeter registered quasi-periodic waves of "hiss" type which have been simultaneously observed in the two hemispheres and which propagate up to the equator (see the orbits 884_0 and 885_0). These waves are observed during several consecutive half-orbits and this shows their space and time extension.
|Figure 1: Plot of the 4 half-orbits where the quasi-periodic waves are observed. These half-orbits are on the right in green. They are downgoing in daytime.|
Figure 2: Data registered by Demeter in the VLF range with the electric sensors (top panel) and the magnetic sensors (bottom panel) for the 4 half-orbits. The spectrograms are calculated onboard the satellite.
It is too early to obtain results related to the main scientific objective of Demeter because we want to process the data from a statistical point of view. For example, the event shown in Figure 3 will be automatically included in the statistics. The seismic data are simultaneously processed with the Demeter orbits to find events where Demeter is close in time and in space, and a dedicated function of the mission center allows to extract from the data base the most favourable events.
IV International Workshop on magnetic, electric and electromagnetic methods in seismology and volcanology in La Londe Les Maures - France.
You will find more information on the workshop site.
08/11/2004: Start of the scientific mission: Everything is OK.
08/09/2004: Switch ON of the on-board calculator and test of the memory.
08/04/2004: New platform software uploaded.
07/29/2004: Start of the scientific mission is postponed.
The start of the scientific mission, that should have been on the 28th, is postponed at least until the middle of the next week due to a problem with the attitude control of the satellite (a SEU induced a failure in the functioning of a reaction wheel).
07/21-07/27/2004: Electromagnetic compatibility tests: OK.
07/15/2004: Tests of the satellite in the nominal configuration for scientific measurements. At this time a long duration test on several orbits (22 hours) was done. During those tests, IAP and IDP were switched ON for the first time, and RNF also performed its first analysis.
07/08/2004: Deployment of the four booms with ICE sensors: OK
07/07/2004: Deployment of the IMSC and ISL boom: OK
07/06/2004: Switching on and validations of the experiments IMSC (magnetic field), ICE (electric field) and ISL (Langmuir probes): OK
First data are available on the LPCE server.
07/05/2004: Switching on and validation of the BANT onboard computer: everything is OK
06/30/2004: News from the satellite:
The first pass with realtime telemetry download above the Aussaguel TTCET station yesterday at about 13h50' local time (11h50' UT) has confirmed:
- the success of the solar panel deployment operation
- the beginning of the transition to the acquisition/survival mode, pointing to the sun
- the good health of the other functions involved during this phase
- the nominal charge of the battery.
General status of Satellite: Nothing to report, nominal performences and very similar to the expectations
Ground Segemnt status: Nothing to report, nominal
Operations taking place until this evening 17h00':
- uploading of the emitter programming
- download of the recorded telemetry
- openning of the "pyro-vanne" of the propulsion system
- setting of the on-board time
- thermal regulation thresholds change.
06/29/2004: Successful launch of Demeter:
The launch of Demeter, first satellite of the Myriade microsatellite series, has been successful today at 8h30 (french local time) form Baïkonour, by a Dnepr rocket.
The satellite injection took place at 8h45 and the solar panel deployment at about 9h07.
The first positionning, and the received telemetry confirmed the accurate position of Demeter as well as its good health. the solar panel is actually deployed, the SCAO is in MACQ phase 3 mode as planned.
It will takes a few days to be fully functionnal and to begin to provide data to the scientists.
06/26/2004: Launch preparation progress:
06/0425/: positive test of the phone line of the observation site; a complementary test is needed on the video diffusion line by Internet, when the CNES's fire wall filters will be modified; the adress given by Russians works correctly from any PC outside the CNES.
06/26/04: Meeting with Kosmotras and Yuzhnoye Launcher "RAL", led by A.De Leffe:
The launcher authorities have given satisfying responses to all the CNES questions, which led A.De Leffe to declare this review successful (beside, picture of this meeting)
- All the electrical test have been performed.
- Launch final configuration set up foreplanned the 06/28/04
06/28/04 11H00 Toulouse: Video link by internet test between CNES Toulouse and the launch observation site
06/28/04: Meeting between Kosmotras and the payloads responsibles during the afternoon
06/29/04 at 9H00 from Baïkonour: plenary meeting of the flight management committee
And evidently Launch at 6H30 UTC on the 06/29/04
06/2004: Satellites fitting in the SHM module
After AKS-1 withdrawal, the last satellite SAUDISAT-2, co-passenger with Demeter, was fitted in the spatial module (SHM) on june 2004, 18th, then the SHM has been closed, in front of CNES people.
Below, pictures of the operation taken by M. Boddaert.
06/2004: Preparation before the launch
Pyro launcher interface brackets installation;
MLI fitting; Micro-switchs electrical verification;
Separation pyros installation;
Battery final charge up;
Strain gages grounding;
Launcher's SHM module delivered before the satellites fitting from June 15th.
05/2004: End-to-end tests
End of 04/2004: Fligh Aptitude Review
End of 04/2004: Technical Qualification Review
04/2004: Reference tests
02/24/2004: Vibrations tests in Toulouse
01/08/2004: The Call for Scientific Research Proposals Demeter is on the CNES (French Space Agency) web site.
Dead Line for Submission : 1st of May 2004
Contact : AODEMETER@cnes.fr
11/2003: Thermal vacuum tests
04/17/2003: Demeter Payload delivery
After a little more than 7 months integration and validation normally littered with obstacles, the Demeter Payload doned its "sunlight clothes" (pictures below) before its delivery to LATECOERE.