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Document - Newsletter
Earth Online Newsletter - 12 May 2023
This issue of the Earth Online Newsletter covers a selection of the latest news and events from ESA.
News - General News
Introducing Mirko Albani
In this short introduction, ESA's Heritage Missions Programme Manager describes what he likes most about ESA's long term archive of satellite mission data and his role in the programme.
News - Success Stories
How Envisat helped to shape global understanding of Earth’s systems
Twenty years have passed since a ground-breaking European spacecraft designed to deliver unprecedented insight into the planet’s changing environment was lofted into orbit.
Activity - Projects
Dragon 2 Cooperation Programme
The Dragon 2 Programme focussed on the exploitation of ESA, ESA's Third Party Missions and Chinese Earth observation data for science and applications development in land, ocean and atmospheric applications.
Tools - Apps
Heritage Missions app for Android
Download the Heritage Missions application to discover what the missions were about, how it worked and what the elements of the space and ground segment that make these missions unique.
Instrument - Positioning/Navigation
The Precise Range And Range-Rate Equipment (PRARE) was a microwave tracking system on board the ERS-1 and ERS-2 missions.
Instrument - Laser Ranging
The Laser Retro-Reflector (LRR), on board the ERS-1 and ERS-2 missions, was an optical device for accurate satellite tracking from the ground to support instrument data evaluation.
Data - Data Description
ERS PRARE Precise Orbit Product (ERS.ORB.POD/ERS.ORB/PRC)
The precise orbit results from a data reduction process in which all available tracking data (Single-Lens Reflex, radar altimeter crossovers, PRARE range and Doppler data) and most accurate correction, transformation and dynamical models are taken into account and in which high level numerical procedures are applied. These orbits are "optimal" achievable representations of the real orbital motion under the circumstances of tracking situation and the "state of the art" model situation. The precise orbit product for the ERS satellites are the satellite ephemeris (position and velocity vector) including time tag, given in a well-defined reference frame, together with the nominal satellite attitude information and a radial orbit correction. Several orbit solutions are currently distributed: A new set of ORB POD (Precise Orbit Determination - REAPER v2) computed with the most updated model standards for the complete ERS-1 and ERS-2 mission. A previous set of ORB POD (REAPER v1) data already available on the ESA dissemination site since 2014, covering the ERS-1 full mission and the ERS-2 mission up to July 2003. ORB PRC which is the original Precise Orbit dataset computed during the ERS mission operations for ERS-1 and ERS-2. In the new POD dataset (REAPER v2) for the ERS-1 and ERS-2 missions, two different orbit solutions are provided together with the combined solution to be used for processing of the radar altimeter measurements and the determination of geodetic/geophysical products: those computed by DEOS (Delft Institute of Earth Observation and Space Systems), and those generated by ESOC (European Space Operations Centre) using different software (GEODYN and NAPEOS respectively). Careful evaluation of the various solutions of REAPER v2 has shown that the DEOS solution for both ERS-1 and ERS-2 has the best performance and is recommended to be used as reference. See the ERS Orbit Validation Report. For the previous version of the POD data set (REAPER v1), with ERS-2 mission data only up to 2003, three different orbit solutions together with the combined solution are available. These precise orbits for ERS-1 and ERS-2 have been computed at DEOS, ESOC, and GFZ (Deutschen GeoForschungsZentrums) using different software and different altimeter databases. Combined solutions have been created using three individual solutions for each satellite. All orbits were derived using consistent models in the same LPOD2005 terrestrial reference frame. These new orbit solutions show notable improvement with respect to DGME04 orbits (Scharroo and Visser, 1998). Thus, RMS crossover differences of new orbits improved by 4-9 mm. Careful evaluation of the various solutions has shown that the combined solution for both ERS-1 and ERS-2 has the best performance. All POD orbit files (REAPER v1/v2) are available in SP3c format.
Instrument - Laser Ranging
The LRR instrument aboard Envisat was used to accurately determine the orbital height of the satellite.
News - Data Release news
Updated Precise Orbit data (POD) for the full ERS-1 and ERS-2 mission available
The Precise Orbit files (ERS.ORB.POD) for the entire ERS-1 and ERS-2 mission periods have been reprocessed with up-to-date standards.