Jason-1
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Jason-1 was launched on December 7, 2001. The Jason-1 Launch vehicle is a Boeing Delta II 7920. The Delta vehicle is shared with another Nasa mission, Timed, with Jason-1 separated first. The launch site is Vandenberg Air Force Base. Its lifespan, announced for 5 years is already exceeded and the current capacities of the satellite still let forecast good performances. Still developed jointly by Cnes and Nasa, Jason-1 is the follow-on of Topex-Poseidon. Jason-1 is a mini-satellite, based on the Proteus multimission spacecraft bus. All its instruments derive from Topex/Poseidon but limiting their weight and their consumption of energy. Its unchanged orbit, compared to that of Topex/Poseidon allows a continuous acquisition of measurements and thus, further our understanding of many ocean phenomena on the long term. A new concept of satellite control and data processing operations were developed in order to deliver near-real time measurements to an international user community for operational oceanography. The user community thus has an important role to play in sustaining the mission's success in the years ahead through the Jason series of satellites. |
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From the launch of OSTM/Jason-2, in June 2008, the both satellites Jason-1 and OSTM/Jason-2 had one-minute shift (55 seconds, exactly). On mid-February, 2009 (cycle 262), Jason-1 assumed a new orbit midway between its original ground tracks but with a time lag of approximately 5 days with OSTM/Jason-2. In other words, the start time of the Jason-1 and OSTM/Jason-2 repeat cycles differs by approximately 5 days. This new tandem configuration better suits for real-time applications. The former Topex/Poseidon ground tracks are now overflown by OSTM/Jason-2.
After having encountered an anomaly at the end of February 2012 and early in March 2012, Jason-1 was in Safe Hold Mode. Cnes and Nasa management, through the Joint Steering Group, have directed the Jason-1 Project to begin a series of maneuvers to reduce the orbit on a geodetic orbit at 1324.0 km. This orbit is drifting orbit with a cycle 406 days and some sub-cycles of 3.9 - 10.9 - 47.5 - 179.5 days (see details on new orbit parameters).
Contact was lost with the Jason-1 spacecraft on 21 June 2013. At the time of the last contact, the spacecraft its payload instruments were in nominal health and there were no indications of any alarms or anomalies. All attempts to re-establish communications with the Jason-1 spacecraft over the ten days from 21 June to 01 July, from both US and French ground stations, were unsuccessful.
Jason-1 was passivated and decommissioned on 01 July 2013, terminating the Jason-1 mission after 11.5 years of operations (see the official announcement written by Nasa/JPL and Cnes on July 2013).
Further information :
- Ocean surface topography from space (Nasa/JPL)
- Jason-1 orbit change (Nasa/JPL)
- Physical Oceanography Distributed Active Archive Center (Nasa/JPL)
- Jason-1 and 2, the ocean observatory (Cnes)
Missions passées 
