Overflight analysis

Authors:

  • Victor Jungnell

Publish date: 2016-11-30

Report number: FOI-R--4320--SE

Pages: 30

Written in: Swedish

Keywords:

  • Overflight analysis
  • satellite
  • sensor
  • orbit
  • constellation
  • Earth observation
  • optical
  • SAR
  • overflight frequency
  • revisit time

Abstract

As part of ongoing research in the area of Space Situational Awareness (SSA) for the Swedish Defence Research Agency this study has focused on overflight analysis. Overflight analysis is an essential part of the larger subject of SSA. The main purpose of the overflight analyses in this study is to give an idea of how often typical Earth observation satellites have the opportunity to image a given area on the ground. Open sources providing satellite orbital parameters and sensor data are used to design a general overflight model consisting of typical Earth observation satellites and sensors. Analyses of both typical and real-world satellites have provided a statistical overflight frequency for different cases, including a possible future scenario for a Russian satellite fleet. The results show that the overflight frequency increases with constellation size, but that this increase is not as high after a certain number of satellites due to overlapping and simultaneous overflights in large constellations. The overflight frequency also increases with latitude and altitude. Results also demonstrate that satellites with SAR sensors can image areas around 3.5 times more frequently than satellites with optical sensors. This is because of SAR sensors' ability to image regardless of lighting conditions and because the sensor's field of regard is larger. A single typical Earth observation satellite can image an area in Sweden once or twice a day on average, depending on the type of imaging sensor used. The study has also looked at existing and future satellite constellations. These satellites are both government-owned (civilian or military) or commercial, the commercial ones providing data to an open market.