Frequently Asked Questions

  1. Why does this website exist?
  2. Do I need to pay for this service?
  3. Which SAR missions are supported?
  4. What is the format of the XML import file?
  5. How are the computed azimuth and incidence angles defined?

Why does this website exist?

The DLR SAR Calibration Group regularly performs calibration campaigns for which numerous reference targets, i. e. corner reflectors and transponders, need to be aligned. Naturally, this is the reason why we regularly get requests from scientists and other SAR users who need support in aligning their own targets.

This website was created as a response to these requests.

Do I need to pay for this service?

No. Nevertheless, we ask you to register before you can start to compute your alignment angles.

Which SAR missions are supported?

At the moment, the following SAR missions are supported:

  • TerraSAR-X
  • TanDEM-X

The alignment angles (and overpass times) are based on the TerraSAR-X reference orbit (also for TanDEM-X). For the purpose of computing reference target alignment angles, this does not result in a significant angular error for TanDEM-X overpasses as the TerraSAR-X and TanDEM-X reference orbits are very close to each other.

For both TerraSAR-X and TanDEM-X overpasses, the computed overpass times are based on the TerraSAR-X reference orbit. This does not include a possible deviation from this reference orbit during the actual overpass. Therefore, the computed overpass times for TerraSAR-X and TanDEM-X are only accurate within about one minute.

What is the format of the XML import file?

The XML format closely mimics the manual data input mask. You may have a look at an example XML file.

Prior to uploading your XML file, you can verify it against the queries.xsd schema definition file. It also contains all the details with respect to optional elements and possible input values.

How are the computed azimuth and incidence angles defined?

The angle definitions are shown in the following diagrams. They exemplary show a trihedral corner reflector as the reference target, but the definition applies as well to other target types.

Definition of incidence angle
Definition of azimuth angle (descending orbit)
Definition of azimuth angle (ascending orbit)

Please keep in mind that you might need to consider the (local, time-varying) magnetic declination should you align your targets in azimuth using a compass.