| 534 | | = External links = |
| | 554 | = RetroReflector Array (RRA) Characteristics: = |
| | 555 | |
| | 556 | |
| | 557 | PROBA-2 will use the same retroreflector package as was installed on Cryosat-1. |
| | 558 | More information about the retroreflector characteristics can be found in the document "CryoSat-LRR-01 Laser Retro Reflector Technical Description" (V. Shargorodsky/2002). |
| | 559 | PROBA-2 Retroreflector Information Form (29 August 2008, PDF): |
| | 560 | |
| | 561 | (from http://ilrs.gsfc.nasa.gov/satellite_missions/ilrssupretro.html) |
| | 562 | Satellite name Name: PROBA-2 |
| | 563 | |
| | 564 | Contact for retroreflector information: Stefano Santandrea, ESA/ESTEC |
| | 565 | Phone number: +31 (71) 565-4407 |
| | 566 | E-mail address: stefano.santandrea @ esa.int |
| | 567 | |
| | 568 | A prerequisite for accurate reduction of laser range observations is a complete set of pre-launch parameters that define the characteristics and location of the LRA on the satellite. The set of parameters should include a general description of the array, including references to any ground-tests that may have been carried out, array manufacturer and whether the array type has been used in previous satellite missions. So the following information is requested. |
| | 569 | |
| | 570 | 1. Array type (spherical, hexagonal, planar, etc.), to include a diagram or photograph: 7 reflectors (1 central and 6 lateral in a circular arrangement) mounted on a flattened cone. See picture for further details. |
| | 571 | 2. Array manufacturer: Scientific Research Institute for Precision Instruments, Moscow |
| | 572 | 3. Link (URL or reference) to any ground-tests that were carried out on the array: |
| | 573 | 4. Other missions using this LRA design and/or type of cubes: CryoSat-1/2, GOCE |
| | 574 | |
| | 575 | For accurate orbital analysis it is essential that full information is available in order that a model of the 3-dimensional position of the satellite centre of mass may be referred to the location in space at which the laser range measurements are made. To achieve this, the 3-D location of the LRA phase centre must be specified in a satellite fixed reference frame with respect to the satellite's mass centre. In practice this means that the following parameters must be available at mm accuracy or better. |
| | 576 | |
| | 577 | 5. 3-D location (possibly time-dependent) of the satellite's mass centre relative to a satellite-based origin: |
| | 578 | Spacecraft CoM (X,Y,Z) = (-0.0160m,-0.0060m,+0.3810m) |
| | 579 | |
| | 580 | 6. 3-D location of the phase centre of the LRA relative to a satellite-based origin: |
| | 581 | LRA CoM (X,Y,Z) = (+0.2085m,-0.2390m,+0.0102m), LRA MSC (X,Y,Z) = (+0.2085m,-0.2390m,+0.0300m) |
| | 582 | Note: the LRA center-of-mass is offset by 19.8 mm from the reference point (= mounting surface center, MSC) along the boresight of the central reflector. The range finding correction relative to the mounting surface center amounts to +19+/-6 mm, and depends on the angle of position and the spacecraft bearing relative to station SLR, and shall be added to the measured range. |
| | 583 | |
| | 584 | However, in order to achieve (6) if it is not directly specified (the ideal case) by the satellite manufacturer, and as an independent check, the following information must be supplied prior to launch. |
| | 585 | |
| | 586 | 7. Position and orientation of the LRA reference point (LRA mass-centre or marker on LRA assembly) relative to a satellite-based origin: |
| | 587 | 8. Position (xyz) of the centre of the front face of each corner cube within the LRA assembly, with respect to the LRA reference point and including information of amount of recession of front faces of cubes: |
| | 588 | (dX,dY,dZ)_0 = (+0.000m,-0.000m,-0.0480m) |
| | 589 | (dX,dY,dZ)_i = ( +0.0455*cos(p/3*(i-1)),-0.0455*sin(p/3*(i-1)),-0.0285m), i=1,...,6 |
| | 590 | 9. Orientation of each cube within the LRA assembly (three angles for each cube): See design drawing. |
| | 591 | 10. Shape and size of each corner cube, especially the height: |
| | 592 | 11. Material from which the cubes are manufactured (e.g. quartz): fused silica with aluminium-coated reflecting prism faces |
| | 593 | 12. Refractive index of the cube material, as a function of wavelength ? (micron): |
| | 594 | 13. Dihedral angle offset(s) and manufacturing tolerance: |
| | 595 | 14. Radius of curvature of front surfaces of cubes, if applicable: |
| | 596 | 15. Flatness of cubes' surfaces (as a fraction of wavelength): |
| | 597 | 16. Whether or not the cubes are coated and with what material: |
| | 598 | = Proba2 Station DATA = |
| | 599 | |
| | 600 | |
| | 601 | timespan is October 1, 2010 through September 30, 2011 |
| | 602 | You can find the station data [http://ilrs.gsfc.nasa.gov/satellite_missions/list_of_satellites/prb2_stadata.html here] |
| | 603 | = =External links== |
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