NASTRAC
NASTRAC-Nitte Amateur Satellite Tracking Center
Introduction
The NASTRAC is the first and final terrestrial end of a communications link to an object in outer space. Wireless Communication is done with Satellites; hence the ground station serves as the access point on Earth. The satellite dumps the data to the ground station whenever it passes by that area. Main purpose of the ground stations is to track and receive telemetry and image data from satellite for data analysis, and also to control the satellite by commanding. Ground station consists of hardware and software to transmit and receive data reliably. The components include, a computer programmed with orbital-prediction software compatible with the hardware for auto-tracking, a transceiver to transmit and receive data and a TNC to decode the incoming data.
The SGS(Studsat Ground Station) is a part of the student Pico-satellite program. SGS is a proposed satellite tracking facility to be built by undergraduate students. The STUDSAT team will develop a working prototype of Pico-satellite that conforms to the CUBESAT standard of total mass less than 1Kg, with dimensions of 10 cm x 10 cm x 11.3 cm. The main objective of the STUDSAT comprises of taking images of Earth's surface.
The architecture of the SGS is based on its operation and requirement. The following diagram shows the architecture of the ground system. The gain of the antenna, gain and NF of the LNA, the affordable losses in cable and the EIRP were all calculated based on the link budget analysis. The received data undergoes various processes such as amplification, down conversion and demodulation before bifurcating into image data and telemetry tracking data. The image data is further processed based on the end user application and the telemetry data is used to study the health of the satellite. The up-command to be transmitted to the satellite is modulated, amplified and finally directed towards antenna systems for transmission.
Downlink: The down link operating frequency is 437.5MHz. The link is initiated by the ground station. After the satellite receives the Link Establishment Frame (LEF), the satellite starts dumping telemetry data. The communication protocol used is AX.25 (using UI frame). The satellite then waits for a command from the ground station and on receiving the command it will start transmitting the image.
Uplink: The up-link operating frequency is 437.5 MHz. It is a simplex mode of communication between the satellite and ground station. The satellite uplinks the LEF, Keplerian elements( for on-board orbit prediction algorithm) and up-commands.
Data Processing
Primary Processing
* Image Sharpening.
* Image Smoothing.
* Negative of an image.
* Image zooming.
* Histogram generation.
* Histogram equalization.
* Image scaling.
Secondary image Processing
* Map Synchronization
* User defined imaging
Telemetry Display
* The different telemetry data received are:
* Battery charge and discharge current
* Mean anomaly
* Right ascension of ascending node (RAAN)
* Battery voltage level
* Solar cell voltage
* Temperature.
* Modes of operation
