Friday, September 23, 2016

PSLV Rocket to Send Eight Satellites into Orbit on Its Longest Flight

Panoromic view of PSLV-C35 at First Launch Pad. Photo Credit: ISRO

The Indian Space Research Organisation (ISRO) will conduct on Monday, Sept. 26, the longest mission of its PLSV booster that is slated to deliver eight satellites into orbit. The rocket will thunder off from First Launch Pad of Satish Dhawan Space Centre (SDSC) in Sriharikota, at 9:12 a.m. local time (3:42 GMT, 11:42 p.m. EDT on Sept. 25).

The mission, designated PSLV-C35, will last two hours and 15 minutes, what makes it the longest PSLV flight ever. Usually, the booster needs about 20 minutes to place its payload into orbit, but this time it will take much more time to conclude the mission as the satellites will be put into two different orbits.

In order to inject the payload into various orbits during one mission, the engineers will have to shut down and restart the fourth stage of the PSLV rocket, called PS4, twice during the flight. ISRO currently masters this multiple burn technique, testing it in previous two PSLV flights.

“The campaign is in full swing for the launch of the PSLV-C35 on September 26. We have planned to release its different payloads at two different orbits this time. This will be a first multiple orbit launch in a single PSLV mission using the PS4 restart method,” said P. Kunhikrishnan, director of SDSC.

The launch of the mission was originally targeted for August 2016, however ISRO re-scheduled it, not disclosing what was behind this decision.

The mission’s primary payload is ISRO’s ScatSat-1 (Scatterometer Satellite-1) weather satellite. It will be released into space first, approximately 17 and a half minutes after the launch. The spacecraft will be placed into a polar Sun-synchronous orbit (SSO) at an altitude of 447 miles (720 kilometers), inclined 98.1 degrees. Other seven satellites will start to be released also into a polar SSO, but at an altitude of 416 miles (670 kilometers), during the last two minutes of the flight.

The car-sized ScatSat-1 satellite, weighing some 818 lbs. (371 kilograms), is based on the IMS-2 bus. The spacecraft features two deployable solar arrays generating about 750 W of power and is equipped in a Ku-band scatterometer with a mass of around 242 lbs. (110 kilograms). The designed operational lifetime of the satellite is five years.

ScatSat-1 is a weather and ocean tracker, designed to provide wind vector data products for weather forecasting, cyclone detection and tracking services to the users. The satellite is the continuation of the OceanSat-2 mission launched by India in September 2009, to study surface winds and ocean surface strata.

Besides ScatSat-1, the PSLV-C35 mission features two other Indian satellites: Pratham and PISat. Both are box-shaped nanosatellites developed by students.

Built by Indian Institute of Technology Bombay, Pratham is a technology demonstrator weighing around 22 lbs. (10 kilograms). It will be used to estimate the total electron count with a resolution of 0.62 x 0.62 mile (1 x 1 kilometer) location grid. 

Manufactured by the People's Education Society Institute of Technology (PESIT) in Bengaluru, the PESIT Imaging Satellite or PISat, is designed for remote sensing applications. With a mass of approximately 11.6 lbs. (5.25 kilograms), this nanosat will utilize its color camera, named NanoCam, to obtain imagery of Earth's surface with a resolution of about 262 feet (80 meters).

The PSLV-C35 mission includes three passengers from Algeria: AlSat-1B, AlSat-2B and AlSat-1N. They will be operated by the Algerian Space Agency (ASAL).

AlSat-1B, built by Surrey Satellite Technology Ltd (SSTL), is a medium resolution Earth-observing satellite, based on the SSTL-100 platform. It weighs about 227 lbs. (103 kilograms) and will be used for monitoring agriculture, environment and disasters.

Manufactured by Airbus Defence and Space, AlSat-2B is a high-resolution remote sensing satellite with panchromatic and multispectral imaging capability. The 258-lbs. (117-kilogram) spacecraft will allow Algeria to acquire very high quality images that could be uses in a variety of applications like: cartography, management of agriculture, forestry, management of natural disasters and land planning.

AlSat-1N, also known as AlSat-Nano is a three-unit CubeSat built by Surrey Space Centre. With a mass of 15.4 lbs. (seven kilograms), the nanosatellite will be used for demonstration of new and innovative space technologies. It will be operated jointly by ASAL and the UK Space Agency.

One commercial payload will be launched by PSLV-C35 – the Pathfinder-1 high-resolution imaging microsatellite. Developed by Spaceflight Services, the satellite will be operated by a US company BlackSky, for up to three years. Pathfinder-1 weighs some 97 lbs. (44 kilograms) and is the first of two demo satellites (Pathfinder-2 will be send to space in November 2016) for the company’s network of Global spacecraft, slated to be launched in 2017.

“Pathfinder-1 and Pathfinder-2 will serve as demonstration satellites and play a vital role in ensuring that all the necessary functions of the satellites are operating properly. Both are standard Earth observation satellites and will focus on one-meter imaging,” Rakesh Narasimhan, executive vice president and general manager of BlackSky, told SpaceFlight Insider.

Monday’s mission will also loft a Canadian three-unit CubeSat nanosatellite, named CanX-7 (Canadian Advanced Nanospace eXperiments 7), also known as NLS-19. It was built by University of Toronto and weighs approximately 17.6 lbs. (eight kilograms). The tiny spacecraft is a technology demonstrator that will deploy a drag sail to perform experiments to help reduce space debris and for tracking commercial aircraft. 

The four-stage PSLV booster is India’s most reliable launch vehicle. The rocket has been used to deliver more than 40 satellites into space for some 19 countries. PSLV is capable of lofting up to 3.25 metric tons to low-Earth orbit and about 1.42 metric tons to a geosynchronous transfer orbit (GTO).

The rocket uses an Earth-storable, liquid-fueled rocket engine for its second stage, known as the Vikas engine; it was developed by the Liquid Propulsion Systems Centre. The third stage of the PSLV is powered by a solid rocket motor that provides the upper stage’s high thrust after the atmospheric phase of the mission. The fourth stage is composed of two Earth-storable liquid-fueled engines.

The 144-foot (44-meter) tall XL version of the PSLV, which will be used for Monday’s mission, is the upgraded variant of the rocket in its standard configuration. Its thrust is increased by the addition of more powerful, stretched strap-on boosters than on the standard version.

The vehicle has a mass of 320 metric tons at liftoff and uses the larger strap-on motors (PSOM-XL) that provide the capability of hoisting heavier payloads into orbit. PSOM-XL uses the larger, 3.2-foot (1-meter) diameter, 44-foot (13.5-meter) length motors. This version of the rocket carries 12 metric tons of solid propellants instead of the nine metric tons that were used on an earlier configuration of the PSLV.

The PSLV rocket in its XL configuration was launched for the first time Oct. 22, 2008, when it sent India’s Chandrayaan-1 lunar probe toward the Moon.

Monday’s mission will be India’s sixth launch this year and the 37th liftoff of the PSLV booster overall. The country’s next flight is currently scheduled to take place in December when a GSLV rocket will send ISRO’s GSAT-19E communications satellite into orbit. However, the exact date of that launch has yet to be announced.

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