Origin and Development of the German Processing and Archiving Facility (D-PAF) for the ESA- ERS-1 Mission
October 30, 2020
Origin and Development of the German Processing and Archiving Facility (D-PAF) for the ESA- ERS-1 Mission
by Dipl.-Ing. Jörg Gredel, DFD Information Systems department head until 1998, and then head of Strategic Planning and Resources at DFD and EOC until December 2002
Winfried Markwitz has already incisively summarized the most significant events leading up to the establishment of DFD. Reading his retrospect brought back many memories, since Winfried Markwitz was my direct superior from 1967 until his retirement in September 1996.
The implementation and in due course successful operation of the German Processing and Archiving Facility (D-PAF) for ERS-1 had, all in all, a substantial influence on the positive development of the Applied Data Technology department into the German Remote Sensing Data Center (DFD), and it determined the main emphasis of my activities at DFD from the late 1980s into the 1990s. But first a brief look back to the roots of this development:
Since 1976 we– at that time still part of GSOC – were for ESA the National Point of Contact (NPOC) for Third Party Missions (Landsat, SeaSat, etc.) as far as the Earthnet Programme was concerned. As head of the image processing department then, I considered data processing for one of the first satellite borne Synthetic Aperture Radars (SAR) of the SeaSat Mission to have an extremely promising future and I enjoyed the full support of Winfried Markwitz in this assessment. Participation in this mission paved the way for our becoming involved in the topic of SAR image processing through ‘learning by doing’. This topic was important because there were indications in the 1980er that several aerial and satellite borne SAR sensors were on the horizon, some of them part of European projects.
Software for processing the data was developed by MDA, a Canadian company, on behalf of the Canada Center for Remote Sensing (CCRS). It was obtained by ESA and also installed at our facilities on an identical computer configuration. Starting in 1979 we used it on behalf of ESA to process the SeaSat L band SAR sensor data acquired and recorded in Oakhanger (Hampshire, England). Building on experience gained using this SAR processor, we ultimately decided to have much more flexible software developed. With ESA concurrence, DFVLR and CCRS jointly commissioned MDA to develop the Generalized SAR Processor GSAR. When it was ready in 1982, GSAR was used to process SeaSat SAR data and later also data from the European SAR-580 campaign. The latter was a flight programme jointly organized by ESA and Nasa’s Joint Research Center JRC using a Canadian Convair 580 airplane equipped with a multifrequency L-C-X band SAR sensor, along with other instruments.
With the experience gained with the SeaSat L band SAR and the L-C-X band SAR-580 we were asked by ESA in the beginning of 1983 to carry out a study on the subject of “Performance Prediction of an Enhanced GSAR-Processor in View of ERS-1”. The study was led by Livio Marelli (ESA-ESRIN) and J.P. Guignard (ESA/ESTEC). Our study team consisted of J. Gredel, H. Schröter W. Noack, and H. Runge.
The results of this study, which were summarized in a May 1984concluding report, were so promising that Winfried Markwitz and I energetically promoted our internal planning to participate in the ERS-1 mission. When the ERS-1 payload was preliminarily defined end of 1984, ESA began Phase C/D for the entire ERS-1 mission (satellite and ground segment). The ground segment was to comprise, in addition to the central ESA facilities (ESOC in Darmstadt and EECF in Frascati), interfaces to all receiving stations and to four Processing and Archiving Facilities in Italy, England, France and Germany. Because of German interests, close cooperation was agreed between DFD and the former German Geodetic Research Institute DGFI (headed by Christoph Reigber). On behalf of ESA a Phase-B study entitled “The German Processing and Archiving Facility for ERS-1” was jointly carried out. The ESA technical management side was handled by Livio Marelli and Maurizio Fea. Christoph Reigber and I led the study in Germany. The study results were documented in 30 Technical Notes and summarized in a final report in May 1987. Contributions for the study came from about 30 colleagues, primarily from DFD and DGFI, but also from INS/Stuttgart, IPI/Hannover and the Klein und Steckl company. In the end it was used to draw up a project plan for Phases C/D “The German PAF for ERS-1 / Project Plan for Phase C/D” and submitted to ESA in December 1987. It convincingly described how D-PAF would be fully functional well in time before the launch.
Financing D-PAF during the development phase was primarily from national or programme sources, plus a 15% ESA investment. In other words, the ESA mission was developed using the program budgets of DLR institutes, and only the subsequent D-PAF operations were financed under an ESA contract. ESA’s D-PAF Acceptance Review took place on 10 April 1991 at DFD. We had reached an important milestone, and at a small celebration I concluded a speech with the comment to ESA that “The D-PAF is not operational, but it is ready for operations”.
The block diagram of July 1993 shows the configuration of D-PAF for continuous ERS-1 operation. As this diagram says more than 1,000 words, let me simply refer to it here. It also makes clear that all DFD departments were engaged in the development of this project. In this context it should be noted that almost simultaneously with D-PAF the satellite data acquisition department, led by Klaus Reiniger, initiated in cooperation with industry, AWI and BKG the construction and operation of a receiving station in Antarctica: the German Antarctic Receiving Station, GARS O’Higgins for short.
D-PAF began operations a few days after the launch of ERS-1 on 17 July 1991, and already in early October 1991 the first SAR data were acquired and recorded at O’Higgins. In August 1991 the executive board’s public relations department requested a presentation on ERS-1 activities on the occasion of a visit by the federal minister of research, Heinz Riesenhuber (at right). I took on this assignment on behalf of Winfried Markwitz.
Together with Maurizio Fea (responsible for D-PAF at ESA-ESRIN, at left) I described DFD’s ERS-1 activities and presented an ERS-1 SAR image of the coast of Scotland.
This concludes my tale about DFD’s start in the European earth observation satellite programme. It was the beginning of a splendid success story leading on the systems side from D-PAF via D-PAC (for Envisat) and on the organizational side from DFD via the Applied Earth Observation institute cluster (C-AF) to today’s Earth Observation Center EOC.
“At the occasion of your internal celebration and on behalf of ESA I would like to congratulate you and your team for the high degree of professionality achieved in the ERS-1 operations. The end of the latest 14 months contract, in fact, has been reached the 30 June 1993 with the fulfillment of all contractual production figures.
I would like also to recall DLR and GFZ teams that ERS-1 has recently successfully passed the first 10000 revolutions around earth, that ERS-2 will be launched on schedule and that therefore a number of years of further fruitful cooperation are in front of us.”
This gave our dedicated collaboration with ESA a decisively important European perspective for the future.
The block diagram (status July 1993) is from the D-PAF brochure.
A late highlight for me was receiving an invitation 20 years after the launch of ERS-1 to attend a workshop in Frascati entitled “Best of ERS: 20 years of observing Earth”.
Because of my freelance EOC activities I was able to accept this invitation together with two former staff members and colleagues.
