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OTB Payload Profile: RadMon to Measure Radiation in Low-Earth Orbit

The concept behind Surrey’s Orbital Test Bed (OTB) missions is to cost-effectively space-qualify new equipment and generate in-orbit data that can’t be collected by any other means. While the first OTB satellite will host payloads for several clients, the spacecraft will also carry experimental components built and operated by Surrey to help us better plan future missions and evolve our product.

As the first in a series of blogs describing OTB’s payloads, we showcase the radiation sensor, or RadMon.
RadMon sensor
One of the Surrey payloads, the RadMon, is a sensor designed by the Surrey engineering team that is now under development at the Surrey U.K. facility where the OTB bus is being prepared for shipment to Colorado later this year. Our team will integrate the RadMon into the spacecraft before it arrives in the U.S. where integration of additional payloads will occur in preparation for the 2016 launch.

As the name implies, RadMon (radiation monitor) is a sensor that measures radiation in orbit. It will continuously collect radiation data, providing information on the doses to which OTB components are exposed during the mission. Research by NASA has concluded that electronic microchips begin to suffer performance errors with their memory storage in the 15 to 20 krad TID (total ionizing dose) range. These errors can wreak havoc on the function of a satellite or its subsystems.

The RadMon will perform three functions—total dose measurement, particle detection, and dose-rate detection. Dose-rate detection will pick up high and low areas of radiation, helping to spot those regions that have high levels of radiation, such as the South Atlantic Anomaly. The RadMon payload will allow us to plot this anomaly.

Location of the South Atlantic Anomaly
RadMon will transmit its measurements as part of the regular telemetry data stream back to the Surrey ground station throughout the mission. We will collect and analyze the data at our Mission Operations Center in Englewood, Colorado, and further refine our in-house radiation models.

Surrey has performed pioneering work on the radiation environment in the medium-Earth orbit through radiation monitors on the SSTL GIOVE-A spacecraft. Because OTB will fly in a low-Earth orbit (LEO), common for a variety of satellites, RadMon will allow us to take a closer look at the radiation dose received by micro-chips and memory chips in this LEO environment. Designed as a low-cost option, we intend to include the RadMon on many of our missions in the future to help further improve our understanding of the environment in which our satellites operate.

Other sensors can measure LEO radiation levels, but we can never have too much data. Surrey uses many off-the-shelf electronic components for satellite applications in LEO. By analyzing the RadMon data stream over time, we will determine if components in LEO missions are receiving TID lower or higher than expected, thus allowing us to consider innovative ways to improve our designs, either through the use of other, potentially COTS, technologies, or improvement of our current designs.


06 October 20140 Comments1 Comment

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