| Paper: | TH-P1.6 |
| Session: | Radio-Frequency Interference II |
| Time: | Thursday, March 29, 15:00 - 15:20 |
| Presentation: |
Oral
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| Topic: |
RFI and spectrum management: |
| Title: |
The CubeSat Radiometer Radio Frequency Interference Technology (CubeRRT) Validation Mission: Instrument Pre-Launch Testing and Project Status |
| Authors: |
Joel Johnson; The Ohio State University | | |
| | Christopher Ball; The Ohio State University | | |
| | Chi-Chih Chen; The Ohio State University | | |
| | Andrew O'Brien; The Ohio State University | | |
| | Graeme Smith; The Ohio State University | | |
| | Christa McKelvey; The Ohio State University | | |
| | Mark Andrews; The Ohio State University | | |
| | Landon Garry; The Ohio State University | | |
| | Sidharth Misra; NASA Jet Propulsion Laboratory | | |
| | Rudi Bendig; NASA Jet Propulsion Laboratory | | |
| | Carl Felten; NASA Jet Propulsion Laboratory | | |
| | Shannon Brown; NASA Jet Propulsion Laboratory | | |
| | Robert Jarnot; NASA Jet Propulsion Laboratory | | |
| | Kevin Horgan; NASA Goddard Space Flight Center | | |
| | Matthew Fritts; NASA Goddard Space Flight Center | | |
| | Jared Lucey; NASA Goddard Space Flight Center | | |
| | Quenton Bonds; NASA Goddard Space Flight Center | | |
| | Carlos Duran-Aviles; NASA Goddard Space Flight Center | | |
| | Michael Solly; NASA Goddard Space Flight Center | | |
| | Damon Bradley; NASA Goddard Space Flight Center | | |
| | Priscilla N Mohammed; NASA Goddard Space Flight Center | | |
| | Jeffrey Piepmeier; NASA Goddard Space Flight Center | | |
| Abstract: |
The CubeSat Radiometer Radio Frequency Interference Technology Validation (CubeRRT) mission is developing a 6U cubesat system to demonstrate radio frequency interference (RFI) detection and filtering technologies for future microwave radiometer remote sensing missions. CubeRRT will perform observations of Earth brightness temperatures from 6-40 GHz using a 1 GHz bandwidth tuned channel and will demonstrate on-board real-time RFI processing. The system expected launch date is mid-2018, with deployment expected from the International Space Station later in 2018 followed by a one year period of on-orbit operations.
The CubeRRT payload consists of a tri-helical antenna subsystem developed by The Ohio State University, a tunable radiometer front end (RFE) developed by NASA Goddard Space Flight Center, and a radiometer digital backend (RDB) developed by NASA Jet Propulsion Laboratory. RFI detection and filtering is performed using both kurtosis and cross frequency methods in real time in 128 sub-channels representing the 1 GHz bandwidth. Given the on-board processing, implementation of the cross-frequency method is a key challenge, since such methods require on a “flat” passband in order to function effectively. While equalization of the passband can be performed through calibration in ground processing, a full calibration of the observed spectrum can be challenging on-board the spacecraft. To address this issue, a series of “flattening” transformations are performed. The first “Level 1” flattening multiplies the observed 128 second moment spectrum by a fixed 128 point set of constants that do not vary with the observed RF frequency. This step is intended to compensate for any passband shape effects introduced in CubeRRT’s 1-2 GHz IF stage that is common to all RF frequencies. The second “Level 2” flattening uses a set of 128 constants looked up from a 4,480 point table so that passband shape effects that vary with RF frequency can be addressed. Finally, “Level 3” flattening further normalizes CubeRRT antenna spectra by the spectra of reference load observations at the same frequency, so that any passband effects common between the antenna and reference states can be compensated. A combination of flattening operations at Levels 2 and 3 enables any differences in passband shape between the two states to be further removed. Determination of appropriate flattening coefficients for these tables, along with any required variations with temperature or other instrument properties, was a key activity of CubeRRT flight payload testing.
The presentation will review the current CubeRRT status and provide instrument performance results from pre-launch test activities with a particular focus on the radiometric and RFI filtering performance obtained. Plans for on-orbit operations will also be discussed with the goal of demonstrating the capability of performing realtime RFI filtering in ten bands commonly used for microwave radiometry in the range 6-40 GHz.
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