Citation
Abstract
The Opportunistic Multiple Spacecraft Per Antenna (OMSPA) concept seeks to provide smallsat missions with a low-attributed-aperture-fee technique for obtaining routine downlink in a manner that is very low cost to the Deep Space Network (DSN). Unlike traditional MSPA in which the number of spacecraft that can be supported is limited by the number of available receivers, OMSPA makes use of a digital recorder at each station that is capable of capturing IF signals from every spacecraft in the antenna beam within the frequency bands of interest. When smallsat missions see one or more opportunities to intercept the traditionally scheduled antenna beam of a “host” spacecraft, they can transmit open loop during those opportunities. Via a secure Internet site, the smallsat mission operators can then retrieve relevant portions of the digital recording for subsequent demodulation and decoding or subscribe to a service that does it for them. The demonstration discussed in this article was intended to provide prospective smallsat users and the DSN, as the prospective service provider, with demonstrable proof that the OMSPA concept is, in fact, an operationally viable means for obtaining routine downlink telemetry. To do this, the demonstration began by treating Mars Odyssey as a “smallsat” and Mars Reconnaissance Orbiter (MRO) as the “host” spacecraft. Using a specially created Beam Intercept Planning System (BIPS) and a DSN 7-Day Schedule Cross-Comparison (7-DSC) tool, opportunities were identified when Mars Odyssey would be transmitting while in MRO’s ground antenna beam. Existing Very Long Baseline Interferometry (VLBI) Science Receivers (VSRs) were used to record the Mars Odyssey downlink telemetry during these opportunities. The recordings were played back to a secure server outside the Flight Operations Network firewall, but inside the JPL firewall. The demonstration team’s signal processing personnel retrieved the recordings from this secure server and downloaded them to a workstation containing an OMSPA Software Demodulator (OSD) tool that was developed to demodulate and decode the Mars Odyssey signal. Validation of the recovered data was then accomplished by comparing the transfer frames obtained through OMSPA with those recovered via Mars Odyssey’s formally scheduled downlink. The demonstration successfully achieved its intended purpose. All of the above steps were accomplished within an operationally viable timeframe, with at least 99.95 percent of the transfer frames being successfully recovered from each demonstration recording.
Details
- Volume
- 42-200
- Published
- February 15, 2015
- Pages
- 1–27
- File Size
- 3.1 MB