PSLV-C35/SCATSAT-1 MISSION

PSLV-C35 is the 37th fl ight of Polar Satellite Launch Vehicle (PSLV), identifi ed for launching ISRO’s Scatsat-1 and 7 co-passenger Satellites into Sun Synchronous Orbits. In this mission, the Satellites are injected into two different circular orbits; the Scatsat-1 into 725 km with 98.1° inclination and all the other Satellites into 670 km with 98.21° inclination. In addition to the above, as per the requirements of Satellites, the mission ensures different equatorial cross over time in Local Time Descending Node (LTDN) for the Satellites. This is being achieved by correcting the Right Ascension of Ascending Node (RAAN) by 3° after injecting Scatsat-1 into orbit. The orbit for the co-passenger Satellites is achieved by restarting PS4 twice subsequent to the separation of Scatsat-1. The fi rst restart of PS4 will be over the North Pole and the second over the South Pole. For accommodating all the Satellites, special adaptors viz. Dual Launch Adaptor (DLA) and Multi Satellite Adaptor (MSA) are used. PSLV-C35 launch is from FLP, SDSC SHAR.

PSLV-C35 Vehicle Characteristics Vehicle Height 44.4 m Lift-Off Mass 294 t Propulsion Stages First Stage 6PSOM + S139 Second Stage PL40 Third Stage HPS3 Fourth Stage L1.6

PSLV-C35 Mission Specifi cations (Osculating) Scatsat-1 Other Satellites Semi-Major Axis 7103.443 ± 20 km 7048.137 ± 20 km *Altitude 725 km 670 km Inclination 98.1° ± 0.2° 98.21° ± 0.2° Launch Pad FLP Launch Azimuth 140° *wrt. mean equatorial Earth radius PSLV-C35 Stages at a Glance Stage 1 Stage 2 Stage 3 Stage 4 PS1 PSOM (PS2) (HPS3) (PS4) Length (m) 20 8.8 12.8 3.6 2.4 Diameter (m) 2.8 1 2.8 2 1.34 Propellant Solid Solid Liquid Solid Liquid

(HTPB based) (HTPB based) (UH25 + N2O4) (HTPB based) (MMH+ MON3) Propellant Mass (t) 138.2 8.9 41.7 7.65 1.6 PSLV-C35 Vehicle Confi guration PSLV Generic (6 PSOM + S139 + PL40 + HPS3 + L 1.6) Payload Accommodation in PSLV-C35

Scatsat-1

Alsat-2B Pathfi nder-1 Alsat-1B Pisat Pratham

NLS-19 Alsat-1N

Satellite Separation Sequence

T6 T6+37s Scatsat-1 separation T6+1050s

T10+27s T10+37s DLA-U separation T10+67s Alsat-1N separation

T10+77s NLS-19 separation T10+157s Pratham separation T10+167s Pisat separation T10+177s Alsat-1B separation

T10+192s Alsat-2B separation T10+207s Pathfi nder-1 separation T10+400s PS4 passivation  T6 - PS4 Cut-off  T10 - PS4 Restart-2 Cut-off Scatsat-1 Separation, PS4 Restart -1, PS4 Restart-2 and PSLV-C35 Co-passenger Satellites Separation Flight Cut-off of PS4 Sequence Iginition of PS4 Separation of HPS3

Ignition of HPS3

Separation of PS2

Separation of Payload Fairing

Ignition of PS2

Separation of PS1

Separation of 2 Air-lit PSOMs

Separation of 4 Ground-lit PSOMs

Ignition of 2 Air-lit PSOMs

Ignition of PS1 Iginition of 4 Ground-lit PSOMs

PSLV-C35 Flight Events

Events Time (s) Local Altitude (km) Inertial Velocity (m/s) RCT Ignition -3 0.024 451.89 PS1 Ignition 0 0.024 451.89 PSOM 1, 2 (GL) Ignition 0.42 0.024 451.89 PSOM 3, 4 (GL) Ignition 0.62 0.024 451.89 PSOM 5, 6 (AL) Ignition 25.00 2.392 546.40 PSOM 1, 2 (GL) Separation 67.90 22.756 1143.62 PSOM 3, 4 (GL) Separation 68.10 22.894 1147.86 PSOM 5, 6 (AL) Separation 90.00 40.911 1642.71 PS1 Separation 112.74 65.276 2027.86 PS2 Ignition 112.94 65.491 2027.02 Payload Fairing Separation 161.14 115.464 2400.74 CLG Initiation 166.50 120.864 2442.97 Flight Events contd...

Events Time (s) Local Altitude (km) Inertial Velocity (m/s) PS2 Separation 264.20 222.233 4144.35 PS3 Ignition 265.40 223.638 4141.24 PS3 Separation 587.80 580.877 6313.34 PS4 Ignition 746.52 680.576 6184.49 PS4 Cut-off 1015.84 730.092 7485.00 Scatsat-1 Separation 1052.84 730.758 7490.68 PS4-Engine restart-1 4958.02 739.314 7489.37 PS4 Re-start-1 cut-off 4978.56 739.306 7475.54 PS4-Engine restart-2 7906.52 689.731 7527.63 PS4 Re-start-2 cut-off 7925.96 689.752 7521.18 DLA-U Separation 7962.96 689.807 7521.05 Alsat-1N Separation 7992.96 689.825 7521.03 NLS-19 Separation 8002.96 689.826 7521.02 Pratham Separation 8082.96 689.737 7520.94 Pisat Separation 8092.96 689.715 7520.94 Alsat-1B Separation 8102.96 689.690 7520.93 Alsat-2B Separation 8117.96 689.647 7520.91 Pathfi nder-1 Separation 8132.96 689.600 7520.90

Satellites in PSLV-C35

Satellites Mass (kg) Scatsat-1 370 Commercial Microsatellites – 3 Nos Alsat-1B 103 Alsat-2B 116 Pathfi nder-1 45 Commercial Nanosatellites - 2 Nos NLS-19 8 Alsat-1N 7 University Satellites – 2 Nos Pisat 5 Pratham 10 Scatsat-1 Scatsat-1 is a continuity mission of ISRO for Oceansat-2 Scatterometer with enhanced features. The payload is a Ku-Band Scatterometer with a scan rate of 20.5 rpm. Scatterometer provides backscatter coeffi cient (σ°, refl ected energy from ocean surface for a transmitted pulse) which is used to generate wind vectors. Wind vectors data is essential for weather forecasting and prediction of cyclone intensity & movement. Few of the new technologies which are included in the Satellite are programmability of slice resolution, cross patching of critical elements to improve reliability and use of miniaturised digital sub systems with high density FPGA. The Satellite is built on IMS-2 bus. The expected mission life of Satellite is 5 years. Mission Objectives • To provide weather forecasting services to the user community. • To generate wind vector products for weather forecasting, cyclone detection and tracking.

Alsat-1B Alsat-1B is an Algerian earth observation Satellite based on the SSTL-100 platform. The Satellite provides 12-m ground sampling distance, 5-band multispectral (Red, Green, Blue, NIR, Panchromatic) imaging payload with a 150 km ground swath coverage. Alsat-1B is meant for medium spatial resolution and high temporal resolution imaging with a frequent revisit to any point on the Earth to monitor rapidly changing phenomena associated with natural and man-made disasters, agriculture and environmental issues. The Satellite is owned and managed by Agence Spatiale Algerienne (ASAL).

Alsat-2B Alsat-2B is part of an Algerian program based on two similar low earth orbit Satellites for remote sensing, Alsat-2A and Alsat-2B. Alsat-2B mission is an optical earth observation of Algerian territory with a resolution of 2.5 m in panchromatic mode and 10 m in multi spectral mode (4 bands). The major application areas of Alsat-2B include Cartography, town and land planning, Management of agriculture, forestry, water, mineral and oil resources and Natural disasters monitoring.

Pathfi nder-1 BlackSky’s Pathfi nder-1 is a high-resolution (1m) imaging microsatellite (~50 kg). BlackSky is a commercial company of Seattle, WA, USA. The Satellite is the initial demonstration of the Black Sky imaging systems which feature a ground resolution of 1m. The Satellite is equipped with onboard propulsion for orbit maintenance, designed and assembled by Spacefl ight Industries. NLS-19 (CanX-7) The NLS-19 is a technology demonstration nanosatellite for the Space Flight Laboratory at the University of Toronto Institute for Aerospace Studies, Canada. The Satellite will conduct two experiments. The primary experiment is a drag sail deorbit device that can be used on future missions to reduce space debris. The secondary experiment is an ADS-B receiver that is used for tracking commercial aircraft.

Alsat-1N Alsat-1N is a technology demonstrator nanosatellite designed, built and launched as part of the education program for Algerian students.Technology demonstrator Payloads include AstroTube Deployable and Retractable Boom, Compact CMOS Camera Demonstrator and Thin Film Solar Cell. Pisat Pisat is an earth imaging nanosatellite built by PESIT (People’s Education Society Institute of Technology), Bengaluru and its consortium under the technical guidance from ISRO. The Satellite is built on a custom made cuboidal structure of 254 x 226 x 181 mm and carries an imaging camera as payload to capture the earth imagery of 185 km x 135 km area with 90 m/ pixel resolution. The Satellite has an active magnetic control system, Inertial Measurement Unit (IMU) and 4π steradian Sun Sensors for estimating attitude errors and Magnetic Torquer Rods as actuators.

Pratham Pratham is built by Indian Institute of Technology (IIT) Bombay, Mumbai, under the technical guidance and support from ISRO. The objective of the Satellite is to measure Total Electron Count (TEC) of ionosphere over India and Paris with a resolution 1km x 1km location grid. The payload includes an instrument consisting of two monopole antennae transmitting linear polarized waves at frequencies 145.98 MHz and 437.455 MHz for measurement of TEC of ionosphere. Telemetry Reception

During the fl ight regime, TTC Network stations identifi ed along the fl ight trajectory acquire the telemetry from the vehicle. Ground Stations at Sriharikotta, Trivandrum, Mauritius, Troll and Svalbard are confi gured for the mission. Communication links (prime and redundant) are established from these stations to transfer the data to MCC. In real time, Vehicle Data Handling Systems (VEDHAS) at individual stations strip the required parameters for Range Safety and Specialist Display Console systems. Additionally the major events during the fl ight are detected and transmitted for further display at MCC. Subsequent to the injection of the Satellite, Preliminary Orbit Determination is carried out and provided to Satellite Team for further tracking and acquiring. Post fl ight, full telemetry data acquired from all the stations is transferred to SHAR ground station and handed over to Project within stipulated time. CBS+NES Stacking PS1 Segment Assembly PSOM Stacking

Glimpses of Pre-Launch Operations

PS2 Stacking PS3+PS4 Moduling

PS3+PS4 Module Stacking Scatsat - 1 Testing Vehicle at Launch Pad

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