ELEC9764 Ground Segment and Satellite Operations

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ELEC9764 Ground Segment and Satellite Operations

Assignment Term 1, 2024

This assignment has two questions of equal value.

Question 1) Satellite visibility and Doppler analysis

Apart from geostationary and geosynchronous orbits with small inclinations, the use of satellites is complicated by the changing visibility of the spacecraft. This means that any ground station is required to determine when satellites will become visible, the azimuth and elevations of the satellite during its visibility period, as well as the expected Doppler frequency offsets during the visibility interval. Two Line Elements (TLEs) are orbital elements that permit the satellite positions and velocities to be propagated from a given time epoch using orbit propagators such as SGP4. The accuracy of the positions and velocities are approximately within 1 km at the epoch and degrade at a rate of about 1 to 2 km per day. TLEs are generated by the US Combined Space Operations Center (CSpOC) for many items in orbit.

In this assignment, you have been provided with the Two Line Elements for a satellite, as well as the location of a ground station and a start time. Your task is to write MATLAB code that uses MATLAB Toolboxes (such as the Aerospace Toolbox) to calculate satellite visibility and other related quantities. The commented MATLAB source code forms part of the assignment. You are also required to produce plots showing satellite positions, range-rates, Dopplers, etc.

1. Create some MATLAB code using the Toolboxes that are available in MATLAB 2021b or later versions to determine the ‘satellite visibility intervals’ within 48 hours of the start time, where a ‘satellite visibility interval’ means a time interval when the satellite is within sight of the ground station. Produce a table showing the time intervals that the satellite is visible. Select the longest time-interval or longest pass for the remaining parts of the assignment.

2. For the longest pass, produce MATLAB code that calculates the azimuth and elevation of the satellite as it passes over. Produce plots of azimuth and elevation for the satellite for that pass. Also produce a plot showing the angular rate at which the satellite passes overhead (i.e. at which rate would a high gain antenna need to rotate to keep the satellite within its main beam).

3. For the longest pass, produce MATLAB code that calculates the range-rate and the Doppler frequencies for the satellite. Assume that the satellite transmits at a frequency of 2200 MHz. Produce plots showing the range-rate over that interval, as well as the Doppler experienced at 2200 MHz. At which point during the pass does the Doppler frequency have its lowest magnitude? How does the maximum range-rate magnitude compare with the maximum range-rate magnitude as estimated using the formula given in the lectures?

4. Assume that the 2200 MHz link transmits a 0.1 W signal from the satellite to the ground station with a bandwidth of 5 MHz using a patch antenna with a gain of 3 dBi. Produce a plot of the C/No value at the ground station using an antenna having a gain of 3.0 dBi and an effective noise temperature of 350K.

TLE to be used for the assignment

TERRA
1 25994U 99068A 24062.77916448 .00000616 00000+0 13909-3 0 9998
2 25994 98.0611 129.3523 0001784 16.2906 94.5691 14.59580843287643

Ground Station Location is Tidbinbilla in the ACT

% CSIRO / NASA / JPL
% Tidbinbilla, Australian Capital Territory, Australia
% Latitude, Longitude, Altitude
35°24′05″S, 148°58′54″E, 550 m

Start Time for the Simulation is:

% This TLE has an epoch of 62.77916448 days into 2024, so select a
% date and time close to this!
2 March 2024, 00:00:00 UTC

Question 2) Ground Station Design

The decrease in the cost of satellite launches has resulted in universities and start-ups building and operating CubeSats. This in turn has driven a need for ground stations for these space assets.

You have been hired by a start-up that requires a ground station for the 6U CubeSat it is building for a low earth orbit mission. Your job is to undertake a study into the development of an in-house ground station, rather than using a commercial service such Satellite as a Service AWS Ground Station.

As part of this study, you need to select a ground station software, a transceiver radio, a modem and antenna. You can also recommend a compatible radio for the spacecraft, although you should ensure that the radio is a ‘capable’ one with a generous downlink capability. Assume that your company has a location where the ground station can be located. In your report include any analysis of what you considered during the selection and the reasons for your selection. Also include a short section detailing the requirements you are attempting to meet with your design.

Your ground station design report should be no longer than 2000 words.

Note

Your assignment is to be submitted as a technical report. The writing style should be clear, effective and conform to that in general use in technical reports. Correct grammar and spelling should be used throughout the report.

Figures and tables should be fully and correctly labelled, e.g., Figure number, title and (if necessary) a reference. All text, diagrams, ideas or other information which did not originate with you should be clearly identified and the sources properly cited and referenced. The report will be checked for plagiarism.

The final report is due on Moodle by Friday, 26 th April and is worth 30% of your course grade.

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