Technology > Calibration
The Rosamond Corner Reflector Array (RCRA) is located near the south beach of Rosamond Dry Lake Bed, California, USA.
Instrument: Rosamond Calibration Array
A typical 2.4-meter Rosamond trihedral corner reflector
The array consists of trihedral corner reflectors (CRs):
- Twenty-three 2.4-meter CRs
- Five 4.8-meter CRs
- Ten 0.7-meter CRs
- The 2.4-meter and 4.8-meter CRs are in a 91° line with respect to each other
- The 4.8-meter CRs look east with an azimuth heading of 350°
- The 0.7-meter CRs are in an 80° line: four have an azimuth heading of 350° and six have a heading of 90°
- Ten of the 2.4-meter CRs look east with an azimuth heading of 350° and the remaining thirteen 2.4-meter CRs look west with an azimuth heading of 170°
Mesh for the 2.4-meter corner reflectors
- 2.4-meters CRs: constructed with Aluminum Alloy 3003 H14 aluminum perforated sheets with staggered round holes of size 0.09375" (2.4 mm).
- 4.8-meters CRs: also constructed with Aluminum Alloy 3003 H14 but with larger 0.5" (12.7mm) round holes, and 48% open surface area. The larger holes in the 4.8-meter CRs allow for lower weight but still compatibility with L-band wavelength.
- 0.7-meters CRs: constructed with 12 (2.053 mm) gauge aluminum solid sheets.
Group photo after assembling a 4.8-meter corner reflector
Group photo after assembling the first 0.7-meter corner reflector
The coordinates listed here are in IGS14 Reference Frame. Please view a chronology of reference frames. The coordinates are expressed as WGS-84 geodetic latitude and height above the reference ellipsoid such that:
- a = 6,378,137 meters
- f = 1/298.257222
Furthermore the coordinates are referenced to epoch 1-Jul-2011 and modeled with approximately 2.4 cm/year of plate motion with an azimuth direction of 283°. Specifically the change in East, North, and Vertical is modeled as:
- delta_east_in_meters = -0.023491 * ( gps_time_past_1-jul-2011_in_secs) / 365.25 / 86400
- delta_north_in_meters = 0.005248 * ( gps_time_past_1-jul-2011_in_secs) / 365.25 / 86400
- delta_vertical_in_meters = -0.000670 * ( gps_time_past_1-jul-2011_in_secs) / 365.25 / 86400
These rates are from the multi-year time series analysis of the permanent GPS monument located in Rosamond, CA. Please find further information here.
L-band image of 350° heading corner reflectors
Accuracy & History
As of November 4, 2015, the location of the bottom vertex of CRs #04 through #12 and CRs #15 through #27 have been surveyed to an accuracy of 2 cm RMS. Several CRs on the west end of the array, specifically CRs #00, #01, #02, #03, #13, and #14 have yet to be surveyed to this accuracy and are believed to be known to around 10 cm RMS.
Due to excessive erosion in the lakebed, CRs #16 and #05 were moved in 2014. CR #16 was moved September 4, 2014 approximately 6.8 meters east of its old location and CR #05 was moved November 4, 2014.
During August 8, 2017 maintenance:
- Found two overturned CRs, #18 and #12.
- #12 was moved ~3 meters north and 2 meters west of its original location.
- #18 was moved ~ 1/4 meter north and ~3 meters west of its original location.
- Sloping elevations required re-adjusted tilts of CRs #11 and #01.
During December 21, 2017 maintenance:
- CRs #00 and #01 were re-aligned and small changes to their positions were necessary. The position of these CRs were remeasured.
- The position of CRs #02, #03, #13 were remeasured.
- Elevation tilts to all the 170 CRs were remeasured.
- As of this time, the position of CR #14 and #15 are still suspect (> 10 CMS), and the tilt of CR #17 is also suspect.
During June 27, 2018 maintenance:
- 0.7-meter CRs #29, #30, #32, #33, #35, #36 were installed on the Lake Bed. These CRs are all facing South to accommodate Ka-band calibration.
- Guy wires for CR #20 were re-secured to the ground.
During November, 2018 maintenance:
- Placed PARC at CR#17 location on November 1, 2018 and then repositioned 2.4-meter CR#17 15.6 meters West and 5.8 meters North of its prior location on November 7, 2018.
- Resurveyed 2.4-meter CR#01, CR#02, CR#03, CR#04, and CR#12.
- Removed 0.7-meter CR#33 from Rosamond Dry Lake Bed.
Next maintenance will be June 2019 to resurvey CR#00, CR#06, CR#07, CR#08 and replace CR#33.
Jet Propulsion Laboratory
Mail Stop 300-238
4800 Oak Grove Drive
Pasadena, California, 91109-8099
Tel: (818) 354-0717
Fax: (818) 393-6440
Corner Reflector (CR) Data
Retrieve corner reflector data (latitude, longitude, orientation, etc) for a particular date. Data goes back to Jan 1, 2000. Output is a comma-separated values (CSV) file.