Subject: No 0150 : Re: No 0149 : Jason 1 status [ The following text is in the "iso-8859-1" character set. ] [ Your display is set for the "US-ASCII" character set. ] [ Some characters may be displayed incorrectly. ] ****************************************************************************** DORISMail 13-Dec-2001 17:22:15 Message No 0150 ****************************************************************************** Author: "Michel Lefebvre" Subject: Re: No 0149 : Jason 1 status bonjour c est bon de relayer des infos comme cela nous avons eu la chance d 'avoir vécu cela en live chaque operation etait annoncée une fois faite le compte rendu arrivait avec DES VRAIES DONNEES des images et une "pédagogie" cela doit y être encore le site indiqué renvoie en fait à www.jason.oceanobs.com ex altimetre apres la mise on ce sont des vraies données qui sont apparues pour Doris c est vraiment super : lire le commentaire je profite de cette occasion pour vous recommander la lecture du site www.Bureau-des-longitudes.fr et en particuloer le pv ecrit à la main de la première reunion du bureau signatures intéréssantes!! et dans le chapitre histoire cliquez sur fondation vopus retrouvez le discours du citoyen abbé Grégoire à la Convention c esttellement "actuel" que j en ai fait une version avec sous titres >> fichier attaché greglef4 ----- Original Message ----- From: "Pascal Willis" To: Sent: Thursday, December 13, 2001 4:12 PM Subject: No 0150 : No 0149 : Jason 1 status **************************************************************************** ** DORISMail 13-Dec-2001 16:04:13 Message No 0149 **************************************************************************** ** Author: Pascal Willis Subject: No 0150 : Jason 1 status 12/12/01 JASON 1 status after 5 days in orbit Launch The launch occurred at the exact targeted time, December 7, 2002 at 15 :07 :35.57 UTC. The injection orbit was very accurate as the actual error was 94 meter on semi major axis and 0.004° on inclination. The satellite orientation at injection was also consistent with the expected one. Satellite initial configuration phase After separation the on-board software has been activated, it initiated the automatic sequence which performs satellite initialisation and which rotates the spacecraft in order to put it in the stable configuration of a slow rotation around the sun direction along the longitudinal axis (this is the mode called safe hold which would be reused in case the software would detect a problem on board later in the mission). At the beginning of this phase the solar array was deployed, this was rapidly confirmed by the gyro metric measurements and by the power signal coming from the solar cells. The convergence of the sun pointing mode (2h30) was very fast with respect to the expected duration thanks to the low initial angular velocities delivered by the launcher, thanks to the efficiency of the attitude control law and to the accuracy of the sensors used in this mode (sun sensors and magnetometers). Earth pointing mode acquisition The equipments necessary for the nominal earth pointing mode were activated from the ground and their good functioning verified on December 8. The gyros, as expected, have reached their full performance after 30 minutes. The star tracker was configured and then went in the tracking mode. Despite the non optimal configuration due to the earth sky transitions which occurred in its field of view in this "barbeque" mode, acquisition of full attitude measurement was acquired in less than one second. Since that time tracking is maintained, only short acquisition periods are observed, they were expected and are perfectly correlated with the perturbations due to the south Atlantic anomaly over fly and to the moon passing in the field of view. The platform GPS was powered on in heliocentric pointing and the cold start was successful within 22 minutes. Since that time the Kalman filter is active and delivers continuous tracking data, more than 4 satellites of the GPS constellation are acquired almost all the time. Change from sun pointing to anti earth antennas has been correct with a 30 sec unavailability period which was expected. Earth pointing mode was comanded on December 10 at 4 :51. During transition to earth pointing, the solar array drive mechanisms were activated. They began to follow the expected control law as expected. All the signals going through these mechanisms are transmitted correctly and in particular the power signal coming from the solar array are perfectly transmitted to the platform. Preliminary analysis of telemetry shows that attitude control performances are well within the specified requirements. This was later confirmed by the altimeter measurement analysis. On board computer and on board software are perfectly working. All along this sequence all parameters indicate that power management subsystem has a good functioning. Power delivered by the solar array and power consumption is exactly as expected Concerning the thermal control, transitions between modes are nominal and the stabilized temperatures obtained in the normal mode are consistent with the expected values as is the associated power consumption. The ground automatic guidance telecomand generation has worked properly. A first set of commands to perform a two thrusters burn has been generated and successfully executed. This test maneuver was associated with a large attitude rotation to reach an in orbit plane attitude. Payload turn on DORIS was powered on December 8 at 18 :19. the first measurement was acquired over the Toulouse beacon 15 minutes later. The main new features of this sensor with respect to the TOPEX/POSEIDON sensor have been successfully tested. The receiver performed autonomous time and orbit acquisition using the timing signal emitted by the Toulouse beacon and then all the DORIS network. First analysis of the measurement performances confirm the expected significant improvements in measurement accuracy. The other payload sensors were activated after earth pointing acquisition on December 10. The TRSR, precise GPS receiver was switched on and acquired satellites from the GPS constellation without difficulty. The radar altimeter was powered on when overflying the mediterranean sea at 20 :15. It went rapidly in tracking mode and first waveforms were acquired over between the Mediterranean and Black seas, in the same location its mythic ancestor was sailing toward the golden fleat quest accompanied by the Argonauts. These first measurements, along with the calibration which have been made, show a very good functioning of the sensor. Tracking over ocean and a large part of earth surfaces is maintained. First evaluation of measurement noise shows better than required performances thanks to the very good signal to noise ratio of the received signal. Then the radiometer was switched on, preliminary analysis of the data show a good functioning of this sensor. This has marked the end of the satellite in orbit configuration initialisation. Which has been performed within less than 78 hours. Ground system Jason ground system robustness has proved to be efficient to conduct operations. In particular the benefit coming from the combination of NASA and CNES facilities has been illustrated. Operational coordination and data exchange between the various teams has been very effective. The performances of the satellite to ground link are very good so that visibility passes are longer than expected and commanding easier. This has allowed to overcome some difficulties which have been faced in the functioning of the earth terminals. First the Aussaguel and Hartebeetshook terminals could not acquired the telemetry signal which was hopefully successfully acquired by Poker Flat and Wallops stations. This problem was rapidly investigated and corrected so that from the 3rd Aussaguel pass functioning of these terminals has proved to be very good. At the present time operations are somehow perturbed by difficulties to correctly acquire the telemetry from Poker Flat and Wallops earth terminal, this is under investigation so that a fix could be done in order to have a better downlink of the science telemetry. The measurement already collected have been processed by the SSALTO mission center which has generated in a test mode the first preliminary science products. The functioning of the processing software is then validated, performances of the products will be evaluated later when the first science products will be available for distribution (which requires at least the accomplishment of the station acquisition maneuvers). Future activities On December 12, we can say that the satellite and ground system have shown a very good functioning and preliminary indications of good performances. Operations planned in the next weeks are the maneuvers which will lead to the rendez vous with TOPEX/POSEIDON mid January. Jason will then fly for several months at a 1 minute separation time from its predecessor. In orbit acceptance activities should confirm this very good preliminary results. The acceptance review is planned beginning of february it will be followed by the science verification phase. Philippe Escudier Jason project manager CNES To get the latest news on the mission you may consult the Jason web sites at CNES and JPL and in particular the http://jason.cnes.fr site.