Technical advancements in embedded systems, sensing technology, and an understanding of the Earth's atmosphere have allowed us to deploy satellites for various applications. A more recent phenomenon is the use of low-Earth (<2,000km from Earth) and medium-Earth (between 2,000km and 35,000km from Earth) orbits to deploy smaller satellites called nanosats to perform applications such as surveillance, mapping, estimating sea levels and areas of forests and lakes. Most of these satellites use GPS to localize themselves. A unique challenge at the scale of a nanosat is that the size, weight, and energy required to run a typical GPS receiver might be more than what is affordable for long-term operation.
The work explored in the following paper focuses on the energy consumption of a typical GPS receiver and its operational challenges in a nanosat setting. The challenges include: power draw of a typical GPS receiver could be as high as 20% of overall power consumption; high-speed travel of nanosatellites (~7.8km/s) and relative speed to the GPS satellites (which themselves travel at 3.8km/s) makes getting a fix with a GPS satellite very challenging with high Doppler shift; lack of attitude control (typical of low power satellites) results in loss of GPS signal and corresponding loss in a fix; and, small delays result in large error requiring precise computation at low power.
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