SAR magnifying glass

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Model of SAR-Lupe and Kosmos-3M upper level

SAR-Lupe is a German satellite reconnaissance system. It consists of five identical small satellites and a ground station ( earth station ) for satellite control and image analysis. It is the world's third reconnaissance system with synthetic aperture radar technology (SAR) , which can deliver high-resolution images from any point on earth regardless of weather and time of day . Before that, such systems were only in use in the USA and Russia , and now also in Japan and Italy . The global exploration system has been usable since December 2007, and the full range of services was achieved in 2008.

technology

General values ​​for the satellites

The satellites were in the years 2006 to 2008, Russian Kosmos-3M - launchers from the space center Plesetsk (northern Russia) into all accommodated. The first satellite has been in orbit since December 2006 and was successfully put into service in January 2007. Further satellites followed SAR-Lupe 2 on July 2, 2007, SAR-Lupe 3 on November 1, 2007, SAR-Lupe 4 on March 27, 2008 and SAR-Lupe 5 on July 22, 2008.

The weight of a single satellite is approx. 720 kg, its size is given as 4 × 3 × 2 m. The estimated service life is at least 10 years, with an expected reliability of 97% per year. The average power consumption is given as around 250  watts .

The satellites orbit in three different orbital planes on near-polar orbits with an inclination of 98 degrees and an average orbit height of 500 km.

Since both the solar cells and the directional antennas are not pivoted on the satellite, the satellite must be aligned differently depending on the mode of use. The alignment takes place with the help of magnetic coils and reaction wheels . In addition, hydrazine thrusters are used for orbital control.

Imaging procedures

radar

The satellites use Synthetic Aperture Radar (SAR), with which images can be obtained regardless of light and weather conditions. The SAR technology allows a significantly higher resolution than a comparable normal radar by taking multiple images of a target from different angles and with appropriate post-processing of the data. The pulse repetition frequency for a recording in the "high-resolution mode" (spot light) is emitted for approx. 11  seconds in succession in a point-by-point focussed manner, the power output is subject to confidentiality . The parabolic radar antenna has a diameter of approx. 3 m and is immovably mounted on the satellite, so it must be rotated completely to aim at a target.

Compared to optics, radar technology has other advantages for military reconnaissance in addition to being independent of the weather : differences in altitude can be better measured and movement speeds can be determined. Since radar waves are reflected particularly well by water and metal, people and technical devices (e.g. vehicles or mines ) can be recognized particularly well. Sometimes trees or camouflage nets can also provide information. However, it is technically possible at least, using a jammer ( Jammers impede or) the radar to block all.

Operation modes and the "magnifying glass" ability

The overflight can take place in the modes 'Strip-Map' (normal, speed over the ground approx. 7 km / s, suitable for large-area observation) and 'Spot-light' (high-resolution): with the latter, the satellite rotates so that the Movement relative to the floor is (at least partially) compensated and thus a higher resolution can be achieved.

The name “magnifying glass” comes from the ability to record particularly interesting targets with a significantly higher resolution. According to the manufacturer, this is so far unique. This is made possible u. a. by combining SAR technology (possibly with two or more satellites at the same time) and the spot-light maneuver in conjunction with the image processing software that summarizes the parameters. When using the magnifying glass, from a physical point of view, in particular, every movement of the target has a negative effect on the resolution, so the target object should be as static as possible. It is not publicly known how the spot-light maneuver in particular affects energy consumption and data volume (storage space and transmission bandwidth). The time required to bring the satellite back into the recording position and how often such a drag maneuver can be carried out are also unknown. Spin stabilization and trajectory control operations continuously consume energy, which can be partially offset by solar cells.

resolution

Resolutions of less than one meter can be achieved in magnifying glass mode . This information may only refer to the vertical resolution (along the flight direction). It should be noted that the angle of inclination of the satellite to the target area also influences the resolution. According to the manufacturer, the resolution is higher than that of American and Russian radar satellites. The manufacturer's example photos have edge widths of 5.5 km × 5.5 km for "highest resolution" and 60 km × 8 km for "high resolution". The width should actually be limited by the radar technology, the length (in strip map mode) either by the internal data processing or the power supply. What is certain, however, is that real area coverage is only possible with significantly more satellites; a limitation that every satellite system has. Exact details of the resolution regarding altitude and speed are not publicly available.

It has already been announced that there is a previously unknown burial site in the natural ground under a German ISAF field camp in Afghanistan , which the SAR-Lupe found in 2007.

Ground station

The ground station was built from 2004 to 2006 in Gelsdorf near Bonn .

The ground station is divided into two segments, the user (NBS) and the satellite ground segment (SBS). The former essentially takes over the target selection and evaluation of the images, the SBS takes care of the technical control, data exchange and image generation (the satellite does not do any preprocessing itself, but only provides raw data).

Transmission of the data to the ground station

A connection to the ground station is generally only possible if the satellite is directly above it. For this reason, the recorded data must first be saved before they can be transmitted to the ground station and processed further. Due to the available on-board memory of around 128  GB , the number of images per day is limited to approx. 30 (this limitation may also be set by the power supply or transmission bandwidth).

The X-band is used for data transmission ( the radar is transmitted via the same parabolic mirror ), control and telemetry data are encrypted and exchanged via S-band (directly with the ground station or via an inter-satellite link).

The average response time (time from the request to the return of the images) is 11 hours, but 95% of the requests will take up to 19 hours. There is no public knowledge of a possible drastic reduction in times through telemetry ships or mobile stations, as is the case with the USA and Russia standard, but the Bundeswehr is planning another ground station in Kiruna , Sweden , in order to be able to transmit data more quickly.

Remarks

All technical values ​​for performance are given in the publicly accessible sources only with minimum values. It may well be that the actual maximum resolution is considerably higher. This value may be around 50 cm, roughly twice as high as officially stated.

SAR satellites

SAR magnifying glass 1

The first satellite was delivered to the Federal Office for Defense Technology and Procurement on September 21, 2006 . Before launch, the satellite went through extensive test series in the IABG satellite test center in Ottobrunn .

The Kosmos 3M launcher had to be modified for the launch because the SAR Lupe satellites are too large for the standard version. A special adaptation of the payload fairing helped. The new payload fairing was successfully tested in early 2005 on a flight of the Kosmos 3M with a Russian satellite.

SAR-Lupe 1 was launched on December 19, 2006 at 2: 19.562 p.m. ( CET ) in Plesezk with a Kosmos-3M rocket. The first data was received about 90 minutes later. The satellite has reached its orbit, is stable, reacts to commands and is sending data.

On January 8, 2007, satellite control was transferred to the military ground station. On January 19, 2007, the Bremen-based manufacturer OHB Technology reported that the functionality of the entire image acquisition chain (radar acquisition, position control, transmission, processing) had been demonstrated: in all acquisition modes, images were successfully delivered in the expected quality.

SAR magnifying glass 2

SAR-Lupe 2 was launched on July 2, 2007 at 19:38:41 UTC with a Kosmos-3M launcher from the Russian spaceport Plesetsk south of Arkhangelsk . The radar satellite was deployed around half an hour later in its near-earth orbit at an altitude of around 500 km. A first life signal was received at 20:41 UTC via the Kerguelen ground station in the southern Indian Ocean. As planned, direct contact between the control center and the satellite was established 92 minutes after the launch. SAR-Lupe 2 works perfectly after the first tests in orbit, so that commissioning started during the night. Unfolding the antenna arm was successful.

SAR magnifying glass 3

SAR-Lupe 3 was completed in autumn 2007 and successfully launched on November 1, 2007 with a Kosmos-3M launcher from the Russian spaceport Plesetsk. At this launch, the experimental Rubin-7 / AIS communications payload was on board the rocket as an additional passenger.

SAR magnifying glass 4

SAR-Lupe 4 was successfully started on March 27, 2008 at 6:15 pm CET. The start had previously been postponed twice due to poor weather conditions.

SAR magnifying glass 5

The fifth and, for the time being, last satellite in the system was successfully launched on July 22, 2008 at 4:40 a.m. CEST with a Kosmos 3M launcher from the Plesetsk spaceport in Russia.

History and manufacture

The SAR-Lupe system is considered a low-cost solution: the previous Horus project was canceled because the costs of up to DM 5 billion for the federal government were too high. In 1998 work began on the SAR-Lupe system, which was originally supposed to cost only around 370 million euros. In the Bundeswehr Plan 2008, the current total costs are given as 746 million euros. This was achieved, on the one hand, through limitations in performance (for example, the radar cannot be swiveled, instead the entire satellite must be rotated), but above all through the use of already existing individual parts , the small satellite construction method and the subcontracting of the respective cheapest supplier (less than half of the individual parts come from Germany). The final contract was finally signed on December 17, 2001.

Client

The system is subordinate to the Federal Armed Forces , clients were the German Federal Ministry of Defense (BMVg) and the Federal Office for Defense Technology and Procurement (BWB). The Central Imaging Reconnaissance (ZAbb Aufkl), a spin-off of the “Department of Imaging Reconnaissance and Object Processing” of the Strategic Reconnaissance Command (KdoStrat Aufkl or KSA), operates the user floor segment.

The following departments can use the system:

contractor

The manufacture of the SAR-Lupe system is subject to a consortium of European companies, led by OHB-System AG, which is also responsible for overall management and which operates the satellite ground segment.

The contractors for the satellite bus are OHB-System, Carlo Gavazzi Space, OHB Teledata, STS Systemtechnik Schwerin and RTG Aero-Hydraulic, and for the SAR payload Tesat-Spacecom , Thales Alenia Space, SAAB Space and RST Radar Systemtechnik. In addition to OHB, OHB-System, Carlo Gavazzi Space and EADS are responsible for the ground segment . Cosmos and Rosoboronexport were commissioned for the satellite launches , and DLR GSOC for the start-up and commissioning phase . RST was responsible for the design of the SAR sensors and the development of the SAR processor and other systems to ensure image quality.

Cooperations (E-SGA and FSLGS)

On July 30, 2002 in Schwerin , a cooperation agreement with the French Army closed, the Helios system for optical satellite reconnaissance used. Since the two systems complement each other well, they should be coupled. The interface that enables the French military to access the SAR-Lupe satellites is called FSLGS ("French SAR-Lupe Ground Segment"). In return, the French are providing access to the Helios system.

On December 1, 2006, OHB Technology received the order from the Federal Office for Defense Technology and Procurement to implement the reconnaissance network. The order volume is around 87 million euros.

It is hoped that other EU countries will also participate with additional satellites. The aim is to create a joint education network for the EU in the medium term . This was already taken into account in the technical planning phase: the system is modular and can be easily expanded. The entire multinational system network is being developed under the name E-SGA ("Europeanization of Satellite-Based Reconnaissance").

Successor system

The Bundeswehr plans to purchase three new satellites for around 800 million euros. The overall management of the project is in turn with the Bremen company OHB-System AG. The satellites of the new system, named SARah, are to be put into orbit after delays in 2020 or 2021 and will replace the previous SAR-Lupe satellites after their service life has expired. The three new satellites (two with the previous radar technology, one with a so-called phased array radar ) will be larger and more powerful.

In addition, a satellite for optical reconnaissance is to be purchased for 170 million euros in order to reduce the dependence on France in this regard.

See also

literature

  • Sascha Lange: The first SAR-Lupe satellite in space . In: Strategy & Technology . February, 2007, pp. 14-16, ISSN  1860-5311

Web links

Individual evidence

  1. ↑ Helmut Michelis: Exclusive look behind the scenes: The Bundeswehr is now peering out of space. rp-online.de, August 4, 2008, accessed on March 9, 2011 .
  2. ↑ a b c Bundeswehr plans to use new spy satellites . Spiegel Online, June 26, 2013, accessed June 26, 2013
  3. ^ OHB system: 2nd SAR-Lupe satellite also successfully launched into orbit . OHB, July 3, 2007
  4. ↑ OHB system: Third SAR-Lupe satellite successfully launched into orbit . OHB, November 1, 2007
  5. ↑ OHB-System: The success story continues: SAR-Lupe 4 successfully launched . OHB, March 28, 2008
  6. ↑ Germany's first satellite-based reconnaissance system SAR-Lupe is complete . DLR, July 22, 2008.
  7. ↑ Alexander Szandar: "Strategic reconnaissance: Bundeswehr eavesdropping on the world". Der Spiegel , September 1, 2008, accessed December 10, 2009 .
  8. ↑ Central Imaging Enlightenment. In: cir.bundeswehr.de. Bundeswehr, accessed on January 29, 2019 .
  9. ^ Gloria Westermeyer: The Impact of Private Actors on Security Governance: An Analysis based on German ISR Capabilities for ISAF . Springer Science & Business Media, 2013, p. 133 ( limited preview in Google Book search).
  10. ↑ SAR-Lupe brochure (PDF) at ohb-system.de; Retrieved November 4, 2010
  11. ↑ Reference project: SAR-LUPE . RST, accessed October 17, 2019.
  12. ↑ New reconnaissance satellites will be launched later. In: Hartpunkt.de. January 29, 2019, accessed February 7, 2019 .