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.
During July 25, 2019 maintenance:
- Repositioned 2.4-meter CR#01 5.1 meters East and 1.1 meters North due to excessive Lake Bed erosion.
- Resurveyed 2.4-meter CR#00, CR#01, CR#06, CR#07, and CR#08.
- Placed 0.7-meter CR#33 back on Rosamond Dry Lake Bed and resurveyed. Orientation is no longer 90 degrees, but rotated for a 350 heading. There are now five 0.7-meter solid corners for a 90 degree heading and five 0.7-meter solid corners for a 350 degree heading.
- Adjusted all remaining corners 1.25 CMS North due to Ridgecrest, CA M 7.1 earthquake on July 6, 2019.
During November 14, 2019 maintenance:
- Repaired 2.4-meter CR#00, remeasured, position changes of -1.6/2.2/0.8 CMS change in E/N/V.
- Removed 0.7 meter CR#28 from the RCRA for maintenance.
During October 14, 2020 maintenance:
- Repaired 2.4 meter CR#02 and re-positioned it 6.5 meters East of its prior location. This target was displaced by weather after January 30, 2020, and is not available in the database after March 14, 2020.
First NISAR 2.8 meter corner reflector installed Oct 21, 2020.
- Placed the first NISAR 2.8 meter corner reflector with a 350 degree heading. Surveyed results in the database can be found with the identifiable label CR#41.
- Placed two movable corner reflector builds for an L-band experiment on the Lake Bed. These 2.4 meter corner reflectors have headings 170 and 350 degrees, and the surveyed results can be found in the database with identifiable labels CR#47 and CR#45 respectively. Although these targets are still on the Lake Bed until TBD, they will only appear in the database for October 22, 2020.
Next maintenance will be May, 2021.
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. No tidal adjustments are made to the coordinates, however the entered date applies the plate motion from the nearby GPS site RSTP.
Hours and minutes (HH:MM) are provided to accommodate movable CR experiments, where CRs were moved to several positions in the same day (e.g. on Oct 22, 2020).