Wen Chen & P L Palmer
Traditionally the process of obtaining images from space has been
labour intensive. A request is made and groundstation staff then schedule
an opportunity on their satellite for image capture. Upon download the
image is then sent to the end user. Recent developments in low cost small
satellites has opened the way for many new users of satellite imagery, and
consequently a greater demand. At the same time the reduced cost of
satellites means there are many more satellites that can take images of
the Earth to support this demand. The question arises as to the optimal
deployment of hardware in space and evaluation of the capacity of multiple
satellite systems to deliver imagery to end users.
In the past this question has attracted little research attention, as the
demand has not been near to capacity. With ventures such as the Disaster
Monitoring constellation of satellites, one of the key design parameters is
capacity, and so evaluation is an important factor to be determined. This
paper analyses both the image capture and image download service for
EO satellites in terms of a mean service rate and inter-service-time.
We present a stochastic analysis based upon a geometric model of
satellite orbits. We provide analytic expressions for the probability of
image capture or download within each orbital period, and derive the
probability distribution for inter-operation times. This analytic model is
then verified using simulations based upon the UK-DMC as a case study.
Queuing analysis of multiple spacecraft taking multiple images for end users.