Metop Direct Dissemination
Data direct from satellites
Data, products and services directly from the Metop and NOAA satellites to a user reception station.
14 May 2021
29 April 2020
Metop Direct Readout
The Metop Direct Readout Service provides local user stations with real-time transmission of data, limited to the instantaneous sub-satellite observation.
The data source is the satellite as it passes over the user's field of view. Readout of all instrument data can be achieved via Advanced High Resolution Picture Transmission (AHRPT).
Metop-B and Metop-C provide a full, global Direct Readout Service. Due to an earlier failure of the Metop-A AHRPT side A, the Metop Direct Readout Service no longer supports full global coverage.
In the case of Metop-A, to minimise the risk of failure to the AHRPT-B unit, while still offering the user community a service, EUMETSAT implemented a 'partial' AHRPT service in those areas where the risk of damage from heavy ion radiation is reduced. For southbound passes, AHRPT side B is activated for all orbits over the North Atlantic and European area, starting at around 60°N. The AHRPT is then switched off before the spacecraft reaches the Southern Atlantic Anomaly region at around 10°N.
AHRPT operations are made in ascending orbits, but with more stringent risk reduction measures than applied for the descending passes given the availability of data via the Fast Dump Extract System (FDES) to cover the North Hemisphere. The same operational restrictions still apply over the polar caps and South Atlantic Anomaly.
Multi-Mission Administrative Message (MMAM)
Users wishing to know the daily switch-on and off times of AHRPT and other spacecraft status information should consult the Metop Multi-MIssion Administrative Message in the UNS (click on relevant tab). For help read the Multi-Mission Administrative Message User Guide.
AHRPT data is disseminated in L-Band, with a data rate of 3.5 Mbps. Local data coverage is of a radius of up to 1500 km.
Users operating existing HRPT stations will have to modify their stations in order to receive the 'Advanced' Metop data. The adaptations, whose feasibility and scope depend upon the design of the existing station, will mainly require a modification of the receiver and the processing software. For further information on station equipment consult a manufacturer.
Under nominal operations the Metop Direct Readout data are openly available to all users within the service footprint. For information on access during periods of Data Denial users should consult the Data Denial User Guide.
Key dissemination system
The Metop Direct Readout Key Dissemination System (KDS) is designed to provide registered users in possession of Metop Station Key Units (SKU) with access to their Public Keys. Valid Public Keys are necessary for the operation of the SKU during periods of Metop data encryption. Access the Key Dissemination System.
For help with using the KDS, please see the User Guide for the EPS EEIS Key Dissemination System.
Local processing software and tools
Data received by the Direct Readout station can be processed further. The following local processing software is available under licence from the NWP-SAF:
|Software name||Description||Software Supplier/More information|
|AAPP||ATOVS and AVHRR Pre-processing Package (AAPP) performs the end-to-end processing of Sounding and Imager data from the AHRPT/HRPT direct readout data stream.||SAF on Numerical Weather Prediction|
|RTTOVS||Radiative Transfer for TOVS (RTTOVS) is a very fast radiative transfer model for nadir viewing passive infrared and microwave satellite radiometers, spectrometers and interferometers.||SAF on Numerical Weather Prediction|
Recommendation regarding use of time stamp
The CCSDS source packets transmitted via Metop AHRPT contain the following time stamp information:
- UTC time stamp in the secondary header (aka TMUTC), please see Metop Space-to-Ground Interface Specification, section 220.127.116.11.2, under EPS Technical Notes.
- Satellite Binary Time, abbreviated SBT (aka On-Board Time, OBT_ISP) in the ancillary data field, please see DJD Appendix A7-3 OBT-to-UTC correlation, under Reception Station Design Documentation.
The EPS mission control centre maintains the onboard TMUTC source by uploading OBT-to-UTC correlation coefficients at regular intervals. Typically, the resulting accuracy of the TMUTC time stamp is in the order of +/- 0.007 second relative to UTC. However, this typical performance is not guaranteed and reliance on this parameter is not recommended.
In light of this, it is recommended that users strictly use the OBT_ISP time stamp and perform the translation to UTC in their ground processing via the OBT-to-UTC correlation parameters. These parameters will be sent via the ADMIN message and published on the website. The formula for computing UTC based on OBT_ISP and the correlation parameters are described in the Metop Space-to-ground Interface Specification, section 18.104.22.168.
TD 18 Metop Direct Readout AHRPT Technical Description
Information on the collection of environmental data from data collection platforms (DCP) and its subsequent distribution to users via Meteosat.
HRPT LRPT Direct Broadcast Services Specification
This document defines the specification of the High Resolution Picture Transmission (HRPT) and the Low Resolution Picture Transmission (LRPT) services provided by the METOP satellite.
Multi-Mission Administrative Message User Guide
Definition of the content and lay-out of the MMAM, containing operational information relevant to users of the Metop HRPT direct read out service.