December 29, 2024

PSLV-C60/SPADEX

PSLV-C60/SPADEX Mission :PSLV-C60 vehicle will carry a pair of SPADEX satellites into an eastward orbit. Subsequent to SPADEXsatellites separation, PS4 stage will be restarted twice to reduce the orbit to 350 km circular orbit withchange in inclination/RAAN. The left out propellant in PS4 will be disposed through main enginesfor enabling safety of PS4 stage. The oxidiser will be let out first followed by fuel in a predeterminedsequence of operations. The existing scheme of spent stage passivation by venting the tank pressurewill also be active. Post passivation of PS4, the control of stage is transferred to POEM avionics.PSLV-C60 is the first Vehicle integrated upto PS4 stage at PIF and moved to MST/FLP for Satellitesassembly and Launch.
SPACE DOCKING EXPERIMENT (SPADEX):The primary objectives of SPADEX are to develop and demonstrate the technology for rendezvous anddocking using two small spacecraft, and to demonstrate controllability in the docked condition, showingthe potential for extending the life of the target spacecraft. Additionally, the mission aims to test powertransfer between the docked spacecrafts.The secondary objectives also include post-docking activities where the spacecraft will performindependent payload operations.Mission ObjectivesSpacecraft A SDX01Spacecraft B SDX02The Space Docking Experiment (SPADEX) is a pivotal project byISRO designed to develop and demonstrate the technology neededfor spacecraft rendezvous, docking, and undocking using two smallsatellites. SPADEX will serve as a milestone in advancing India’scapabilities in space docking, a critical technology forfuture space missions including satellite servicing, spacestation operations, and interplanetary missions. By masteringrendezvous and docking technologies, ISRO is set to enhance itsoperational flexibility and expand its mission horizons.
SPADEX Spacecrafts:SPADEX spacecrafts named as Spacecraft A and Spacecraft B are built on an extended Microsat Bus,each with a mass of approximately ~220 kg. These spacecrafts are androgynous in nature i.e. eitherof the spacecraft can act as chaser (active spacecraft) during docking. They are equipped with solarpanels, lithium-ion batteries, and a robust power management system. The Attitude and Orbit ControlSystem (AOCS) includes sensors such as star sensors, sun sensors, magnetometers, and actuatorslike reaction wheels, magnetic torquers, and thrusters.The docking mechanism of SPADEX is motor-driven, featuring capture, extension/retraction, andrigidization mechanisms. There is also a power transfer connector mechanism for experimental powertransfer post-docking and a video camera tilt mechanism for monitoring the docking process. Thedocking procedure is meticulously planned with multiple phases: initial separation and controlled drift,sequentially closer approach phases with hold points for safety and control, and the final docking phasewith capture, retraction, and rigidization.For standalone mission phases after docking experiments, the spacecrafts are equipped with payloads.Spacecraft A is containing with High Resolution Camera (HRC) and Spacecraft B is accommodatedwith two payloads viz. Miniature Multispectral (MMX) payload & Radiation Monitor (RadMon). Thesepayloads will provide high resolution images, natural resource monitoring, vegetation studies and onorbit radiation environment measurements which find numerous applications.Key TechnologiesSPADEX include docking sensors such as the Laser Range Finder (LRF), Rendezvous Sensor(RS), and Proximity & Docking Sensor (PDS) for precise measurement of distance, and attitude.Mechanism Entry Sensor (MES) for initiating docking and Video Monitor (VM) for real time imagingof docking operations.The spacecrafts are also equipped with Inter Satellite Link (ISL) providing realtime transfer of AOCSand navigation parameters between them for relative state estimation.The power system consists of solar arrays generating up to 528 W, supporting continuous loadrequirements, and power transfer mechanisms to test energy sharing between docked spacecraft.The onboard computer (OBC) is a sophisticated system handling command processing, dataacquisition, attitude control, telemetry and mechanism motor drives