Pakistan's Prototype Remote Sensing Satellite (PRSS)
SUPARCO developed a Prototype Remote Sensing Satellite in 2007 as a part of skill development programme. It is an indigenous effort in the field of satellite engineering aimed at enhancing the know-how and capacity building of its scientists and engineers. Facilities developed/upgraded were utilized to test and evaluate the satellite responses in various environments such as HELMHOLTZ Coil, Clean Room, Anechoic Chamber and Light Controlled Environment, Satellite Platform Control Unit and Satellite Mission Control Room.
The Prototype satellite is the evaluation version of FM Satellite, in which Satellite Control, Navigation, Imaging, Communication and Power Management have been completely implemented.
The PRSS is able to acquire 2.5m GSD of satellite images. The PRSS Satellite is controlled through the OBC which can handle Telecommand and Telemetry through Ground Segment. All the subsystems of the Satellite are interconnected through CAN-2.0 Bus. The Power Capacity of PRSS is 600W with state of the art Power Management system which is used to perform Solar Power Distribution, Battery Power Distribution, Fast Take Over and Battery Charging Module and Subsystem Power Distribution through specific Power Control Unit which will manage the power according to specific requirements. In Satellite Navigation and Control system, PRSS is fully equipped with sophisticated Sensors and Actuators. The Satellite Navigation system comprises 3-Axis rate Gyros, Magnetometers, Accelerometers, Digital sun Sensor and Star tracking Sensors in order to provide accurate attitude and orbital determination. Magnetotorquer Rods, Thruster and Reaction wheels are used for controlling satellite attitude. The imaging Payload System is equipped with High resolution CCD sensor which is used in IKONOS, QUICKBIRD satellite for imaging with high speed Data Acquisition and Transmission to Ground Segment. The protocol implementation for communication of PRSS to Satellite Ground Segment is fully CCSDS complaint which can easily be interfaced with any standard Ground based equipments.
The prototype satellite has been integrated and tested under various conditions and through various testing tools in order to evaluate its performance and reliability.
Development Of PRSS Subsystems
On-Board Data Handling System
The On-Board Computer System of PRSS Prototype satellite on 386 Ex Processor based and hardware communication on CAN 2.0 bus. PIC Controllers have been used to establish sub-system communication with On Board Computer (OBC).OBC has been mounted and harnessed with other subsystems on satellite structure. Ground station software functionality with hardwired link has been successfully established and tested along with Telemetry acquisition and Telecommand generation.
The OBC is fully equipped with redundant logic circuits which can handle any kind of error occurring in space.
RF Transmitter / Receiver
Along with digital expertise, PRSS team is also mature in RF areas. The PRSS Prototype is equipped with S-Band transmitter, supporting Data rate of 150 Mbps with direct carrier QPSK modulation scheme. Integration and testing of different transmitter modules was performed successfully. S-Band Telemetry Transmitter and Telecommand Receiver has been mounted on satellite.
Reaction Wheel and Propellant Tank
The reaction wheel mounted on the PRSS is used to perform actuation for compensation of orbital displacement in SPACE environment. The reaction wheel has been designed according to theoretical calculation of satellite environment. The pressure vessel design is essential because the propellant used for the thrusters needs to be stored in some storage device, the pressure vessel serves this purpose.
The storage tank was developed by using ASME Section VIII standards (the standards for pressure vessel). The pressure vessel is designed to store 30kg of propellant at high pressure without failure, with mass not more that of 10Kg.
Satellite Electrical Power System
PRSS Prototype Model is equipped with 600 watts Power System which has been developed and integrated with other subsystems. The power requirements of satellite Prototype comprises Solar panels of 32V and 11A, Battery Pack of 24V and 10A, fully regulated bus of 28V, Battery Discharge Regulators, Battery Charger (Fast and Trickle), Power Management and Control Unit. Separate Power distribution modules have been designed for individual subsystems with the provision of voltage and current monitoring.
Imaging Payload System
Functional testing of Imaging Payload of PRSS has been successfully completed. The Features of the Imaging Payload System are: KLI14403 Tri-linear CCD Sensors are used for imaging which have 3-Band sensor arrays with Resolution of 14400 pixels in line. High rate pixel output has been interfaced with 10MHz, 3-Parallel High Speed ADC with 12 Bit Resolution at 10MHz rate, Imaging Payload Controller on DM642 Media Processor Based Design for Managing System Tasks, Ethernet Based Image Data Transmission with CCSDS format at 100Mbps, UART Based IPC interface with CAN Controller, Telescope with 20m focusing for testing and evaluation of overall performance of sensor.
The Ground Segment Software has been developed for the acquisition of image data from satellite payload controller over Ethernet interface. It acquires and saves image data with time stamping and displays sub-sampled/low resolution image in the GUI. An Imaging Platform is designed to acquire the simulated earth images. Since the PRSS MSS sensor is push broom sensor therefore the moving platform is developed in order to test sensor and overall IPS electronics performance. This system is placed on PRSS Prototype Structure and its harnessing functional testing/debugging has been completed. Its software and hardware performance with power consumption log is measured and scrutinized with calculated system response which has successfully fulfilled all such requirement.
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