Mission Specification

Ocean Surface Topography Mission (OSTM)/Jason-2 is a follow-on altimetric mission to the very successful TOPEX/Poseidon mission and Jason-1. It is a joint mission between NASA and CNES (French space agency). It launched June 20, 2008 and began data collection on July 12, 2008. OSTM is capable of measuring significant wave height, sigma0, dry and wet troposphere and ionosphere, which can be used to calculate sea surface height and anomalies and total electron content.

OSMT has a repeat period of approximately 10 days with 254 passes per cycle. A list of cycle start times can be found here.

Sometimes there maybe anomalous or missing data. Occasionally OSTM must perform maneuvers to maintain orbit. This may cause anomalous values so a list of maneuvers is available here. When the satellite detects something abnormal it will go into safehold and will turn off all instruments and no data will be collected. A list of safeholds and periods of no data collection can be found here.

  • Poseidon-3 – Dual frequency radar altimeter that measures in the Ku (13.575 GHz) and C (5.3 GHz). It measures altimeter range, sigma0, significant wave height and ionospheric correction
  • DORIS – Doppler Orbitography and Radiopositiong by Satellite is a Precise Orbit Determination (POD) system. It receives at the 401.25 MHz and 2036.25 MHz frequencies. It is used for the all weather global tracking and calculates the orbit ephemeris.
  • AMR – Advance Microwave Radiometer measures the 18.7 GHz, 23.8 GHz and 34.0 GHz sea surface microwave brightness temperatures. The 18.7 GHz channel provides the wind induced effects in the sea surface background emissions correction. The 23.8 GHz channel measures water vapor. The 34.0 GHz channel measures the cloud liquid water to be corrected. All together the three frequencies provide the error in the satellite range measurement caused by pulse delay due to water vapor.
  • LRA – Laser Retroreflector Array supports the calibration and validation for the POD.
  • GPSP – GPS Payload receiver. It provides supplementary position data to support the POD function and to improve gravity field models.
  • CARMEN-2 Radiation Detectors – CNES instrument that measures high energy particles that could disrupt the DORIS oscillator and create drifts.
  • LPT – Light Particle Telescope. Provided by JAXA, measures radiation to complement that measured by DORIS.
  • T2L2 – Time Transfer by Laser Link. CNES instrument for precise time transfer used to monitor the clock in DORIS.