The Precise Orbital products and auxiliary data generated by the Copernicus POD (Precise Orbit Determination) Service for the SENTINEL-2 mission corresponds to NRT timeliness, having two different types of products.
- Near Real-Time orbital products (NRT) are generated based on immediate GPS L0 availability with the near real-time GPS orbits and clocks provided by EGP
- Near Real Time predicted (PRE) products are computed a certain time ahead of an astronomical event, particularly the ascending node crossing
Details on the official POD products are available in the File Format Specification document. A brief description of the POD products is included hereafter.
The NRT orbital product (AUX_RESORB) generation is associated to the availability of a new GPS L0 file (SAD PDI), which typically has coverage of an orbit. It contains the latest PVT in the GPS L0 file that triggered its generation plus 2 orbits backwards. Thus, the official POD NRT products for SENTINEL-2 typically show overlaps between 1 or 2 orbits, depending on the coverage of the GPS L0.
The PRE orbital product (AUX_PREORB) is generated at least 90 minutes before the predicted ascending node crossing (ANX) and contains 5 state vectors at the node crossings (i.e., 2 orbits).
Each of these products has different timeliness and accuracy requirements, which are summarised in the following table:
|Requirements of Orbital Products|
|NRT Predicted (AUX_PREORB)||90 minutes before ANX||10 m (2D RMS 3-sigma)|
|NRT (AUX_RESORB)||30 minutes||3 m (3D RMS 1-sigma)|
The timeliness and performance results of the precise orbital products are provided in the Quality Control section.
Additionally, the GNSS L1B RINEX files for SENTINEL-2 are delivered on a daily basis to the PDGS with a latency of 7 days. These files contain the decoded GPS observations (pseudorange and carrier phase) following the International GNSS Service (IGS) RINEX ICD.The SENTINEL-2 GNSS L1B RINEX data products are made available to the user community through the Copernicus Data Space Ecosystem.
Moreover, performing POD requires making use of the satellite attitude Quaternions files and validating the results obtained against an external reference solution. The user community can also find the Quaternions files into the previous link of the ESA Copernicus Open Access Hub. At this moment, there are no orbit products delivered to the ESA Copernicus Open Access Hub from the CPOD Service. If such products are requested by the user community, it will be addressed the possibility to make them also available
The following table summarises the latency and availability of all SENTINEL-2 CPOD Service products routinely delivered to the ESA Copernicus Open Access Hub:
|S-2 CPOD Products|
|Product||Delivery Frequency (prod. per day)||Latency||Mission Availability|
|GNSS L1B RINEX Files||1||7 days||All mission|
|Quaternions Files||1||2 days||All mission|
Figure 1: Example of GPS antenna and receiver on-board SENTINEL-1, -2, and -3