Astrosat India’S First Dedicated Astronomy Satellite
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ASTROSAT INDIA’S FIRST DEDICATED ASTRONOMY SATELLITE K.SUSRYANARAYANA SARMA PROJECT DIRECTOR , ASTROSAT ASTROSAT Mission Overview • Mission : Simultaneous Multi wavelength Astronomy observations visible to hard x-ray • Orbit Altitude : 650 km, Inclination : 6 deg. – near equtorial • Mass :1550 kg • Power: 2100 watts • Payload pointing : 0.05 deg • Slew rate : 0.6 deg/sec • Launch: By PSLV XL, Third Quarter 2015 –From Sriharikota • Operational life : 5 years ASTROSAT Mission Overview • Payloads Instruments: – Large X-Ray Proportional Counter (LAXPC) -TIFR – Soft x-ray Telescope (SXT)-TIFR – Cadmium Zinc Telluride Imager (CZTI) -TIFR – Charge Particle Monitor (CPM) - TIFR – Ultra Violet Imaging Telescope (UVIT ) – IIA – Scanning Sky Monitor (SSM ) – ISAC ASTROSAT Mission Overview • ASTROSAT will be a proposal-driven general purpose observatory. • Open observing time on ASTROSAT will start one year after launch, for which proposals will be invited from the astronomy community. ASTROSAT Instrument Configuration LARGE AREA X-RAY PROPORTIONAL COUNTER (LAXPC) Large Area X-ray Proportional Counter (LAXPC) • sensitive in 3-80 keV band. • consists of 3 identical co-aligned gas filled proportional counter detector units. • LAXPC unmatched X-ray event timing of each photon in 10 seconds Average Effective Area of 3 LAXPCs : About 6000 cm2 Absorber Gas : 90 % Xenon + 10 % Methane Gas Pressure : ~ Two atmosphere (1520 torr) In clean room FOV : 1o x 1o Angular resolution : 1-5 arc min. Energy resolution : 11% @ 22 Kev Time resolution : 10s Sensitivity : 0.1 milli Crab Total weight with electronics Design Challenges: Including bellow : 419 Kgs 1. Building uniform instrument characteristics across an area as large as 6000 cm2 2. Development of highly precise Timing circuit (with a capability of measuring 10 sec) and its interface with Satellite Positioning system. 3. Development of an efficient Gas Purifier to avoid degradation of instrument. 4. Calibration QUALIFICATION OF LAXPC • LAXPC detectors and Electronics Qualified for both Sine and Random vibration specifications • LAXPC detectors and Electronics Qualified for temperature specifications under vacuum. • LAXPC full chain is tested for MIL standard EMI/EMC CS , RS ,CE and RE tests . Results reviewed and cleared. • End- End Calibration done in detail . QUALIFICATION FOR LAUNCH/SPACE ENVIRONMENT Sine Vibration Specifications (3 Axes) Random Vibration Specifications (3 Axes) Frequency Amplitude 2 Frequency (Hz) PSD (g / Hz) (Hz) Qualification level Acceptance level Qualification level Acceptance level 5 – 20 9.3 mm 6.2 mm 20 – 100 + 3 dB / oct. + 3 dB / oct. 20 – 70 15 g 10 g 100 – 700 0.05 0.02 70 –100 8 g 5.3 g 700 – 2000 - 3 dB / oct. - 3 dB / oct. Sweep rate 2 oct. / min. 4 oct. / min. Overall gRMS 8.3 g 5.5 g Temperature Specifications for LAXPC Subsystems Temperature limits C Remarks Non Operating Qualification Acceptance Design Sub system Description Location Temp Min Max Min Max Min Max Min Max gradient/ Heritage Top AS-LX-DT-03 LAXPC-3 Detector -5 45 -5 45 0 40 10 30 Deck LAXPC-1 Processing EP-02 AS-LX-EL-01 -15 55 -15 55 -10 50 0 40 Electronics inside LAXPC Common EP-02 AS-LX-EL-04 -15 55 -15 55 -10 50 0 40 Electronics inside LAXPC Gas purifier AS-LX-EL-05 -15 55 -15 55 -10 50 0 40 Electronics LAXPC Detector Vibration Test LAXPC Detector Vibration Test LAXPC TVAC TESTS LAXPC TVAC TESTS LAXPC Full chain: Detector + PE & STBG on EMI/EMC Table FOV CLEARENCE PAYLOAD FOV* Anti Reflection Sun Avoidance Requirement Clearance on S/c Angle LAXPC 1 deg X 1 deg 15 X 15 deg 30deg Partial blockage of 4 deg in Roll-Pitch Plane for LAXPC 01&02 with UVIT Payload lid in deployed condition. High Precision Timing with LAXPC • Original Requirement of LAXPC payload was for high resolution (10 µsec), accurate (with-in 10 µsec to UTC) & stable (low drift over mission life of ~5 years) event timing capability. • Options were to have space qualified Oven Controller Crystal Oscillator (OCXO,) but found unfeasible due to very high cost and power requirements. • Worked out a detailed scheme to get an Satellite Positioning System (SPS) for ASTROSAT and to use Pulse Per Second (PPS) signal & • The LAXPC Time synchronization scheme achieve high accuracy over the long period of 5 successfully implemented and provides a continuous years while using standard low cost low power & accurate correlation between a) Instrument Time TCXO to get required timing resolution. b) UTC time & C) Satellite OBT time. • Once accurate timing scheme was established • Achieved all the required parameters in terms of for LAXPC, same was made available to other X- precision and stability. ray instruments and thus achieves very good • Event timing resolution of 10 µsec is achieved. timing co-relation between each of the ASTROSAT science payload. LAXPC Detector On-board Gas Purification On-Board Gas Purification of Detectors is planned to be done periodically to regain energy resolution. (once in 4 /5 weeks ) Science Data Handling (High Bit-rate Telemetry) • BDH accepts data from all science payloads at various rates, formats and encodes the same and then transfers to SSR for recording. • Three UVIT channels transfer a burst of 8 bit parallel data @ 22Mbps rate. •Each X-ray channel sends data in serial burst of 2048 bytes at various rates, which are then formatted into interleaved packets of 2160 bytes, RS encoded and transferred to SSR on Channel 4 (Q2) as 8 bit parallel @ 8.8Mhz • Individual payload data is segregated and processed on ground to generate Level 1 and Level 2 products. Ground segment • The Ground Command and Control Centre for ASTROSAT will be located at ISTRAC, Bangalore, India • 12/ 13 contacts every day . 5 min-12 min duration. • The satellite is capable of gathering 420 gigabits of data every day that can be down loaded in 10 to 11 orbits • The primary data archive for ASTROSAT will be located at the Indian Space Science Data Centre (ISSDC) near Bangalore, India. • Data download will be possible during every visible pass over Bangalore. Ten out of 14 orbits per day will be visible to the ground station. ASTROSAT GROUND TRACK ASTROSAT GROUND SEGMENT ASTROSAT Proposal Processing System ( ISSDC ) ISSDC ATAC/ ATC Growing MCAP DATABASE ASTRAL Flight Mission COMMAND Sequence Dynamics Planning GENERATION S/W Payload Sequencer ASSORT SSM Planning S/W Data Processing Level-0/ Archival & Level-1 s/w Retrieval S/W 11mt Bangalore Ground Station Level-2 S/W INDIAN SPACE SCIENCE DATA CENTRE Raw P/L data ingest QLD / AUX / L-0 / L-1 Processing Archival of AUX / L-0 / L-1 / L-2 Dissemination Web Services: Astroviewer, L-2 S/W Execute, APPS, Product for public access (after lock-in period), outreach I/F with: Network stations, MOX, POCs/GO Observational Efficiency • During an orbit satellite will encounter eclipse, source occult, SAA and bright earth conditions. • Payloads are to be reconfigured and operated without violating the constraints: o 12 deg with ram angle. o 45 deg with sun. o 12 deg with bright earth/Repointing while encountering bright earth terminator. o Stand by mode while SAA crossover. • SAA, occult and eclipse may overlap partially. • Observation efficiency expected for ASTROSAT is 30- 35%. Observational Efficiency (Contd...) Observation Phases and Data Policy Instruments PV Phase Guaranteed First Year Second year Third year (6 months)3 Time (next Regular Regular Regular 6 months)4 observations observations observations X-ray Inst. 67% 4 months 32.5% 20% - Teams UVIT Teams 33% 2 months 17.5% 10% - Indian - - 35% 45% 65% proposals International - - - 10% 20% proposals CSA Team1 - - 5% 5% 5% LU Team2 - - 3% 3% 3% TOO - - 5% 5% 5% Calibration - - 2% 2% 2% time Courtesy : SSPO,IRSO HQ Distribution of Guaranteed Time Between X-ray Instrument Teams PV Phase Guaranteed Time First Year Second Year (6 months) (6 months) Regular Regular Observations Observations Total % of 67% 4 months (120 32.5% 20% time for X-ray days) instruments LAXPC 21% 37 days 10.5% 7% CZT 9% 16 days 4% 2.5% SXT 24% 43 days 11.5% 7.0% SSM 13% 24 days 6.5% 3.5% Courtesy : SSPO,IRSO HQ SATELLITE INTEGRATION IN PROGRESS LAXPC INTEGRATION SXT ON DECK UVIT INTEGRATION UVIT INTEGRATION UVIT INTEGRATION PAYLOAD STATUS PAYLOAD STATUS SOFT X-RAY TELESCOPE (SXT) DELIVERED. ELECTRICAL INTEGRATION COMPLETED LARGE AREA X-RAY PROPORTIONAL COUNTER ALL CHAINS DELIVERED (LAXPC) ELECTRICAL INTEGRATION COMPLETED ULTRA VIOLET IMAGING TELESCOPE (UVIT) DELIVERED. ELECTRICAL INTEGRATION IN PROGRESS SCANNING SKY MONITOR (SSM) COMPLETED ALL TESTS READY FOR DELIVERY CADMIUM ZINC TELLURIDE IMAGER (CZTI) PROCESSING ELECTRONICS- READY DETECTOR – UNDER TEST AND EVALUATION CHARGE PARTICLE MONITOR (CPM) READY TO DELIVER schedule ACTIVITY SCHEDULE Bus systems Jan 2015 (Antenna systems ) Payload systems Jan 2015 (CZTI) Disassembled Testing Feb 2015 Assembled testing April 2015 Themovac Test May 2015 Dynamic tests, June 2015 Deployment tests Acoustics Shipment July 2015 Thank you .