India’s PSLV poised for launch with 29 satellites

India’s Polar Satellite Launch Vehicle, fitted with four solid rocket boosters, stands on the Second Launch Pad at the Satish Dhawan Space Center on India’s east coast on the Bay of Bengal. Credit: ISRO

An Indian Polar Satellite Launch Vehicle is scheduled for liftoff Sunday night with an intelligence-gathering electronic surveillance satellite and 28 secondary payloads, including 20 Earth-imaging Dove nanosatellites for Planet, the U.S. company which criticized India’s anti-satellite test for generating space debris last week.

Heading for three different orbits on a marathon mission that will conclude with the rocket’s fourth stage becoming a platform for experiments, the PSLV is set for launch at 0357 GMT Monday (11:57 p.m. EDT Sunday) from the Second Launch Pad at Satish Dhawan Space Center on Sriharikota Island, located on India’s east coast on the Bay of Bengal.

Liftoff is scheduled for 9:27 a.m. Indian Standard Time on Monday.

The PSLV will launch in a new configuration with four strap-on solid rocket boosters, a configuration named the PSLV-QL. Previous PSLVs launched with six, two or zero strap-on motors.

In another first, the PSLV’s liquid-fueled fourth stage carries solar panels to generate electricity in space, providing power to three payloads that will use the spent rocket body as a hosting platform in orbit.

The primary payload is EMISat, an Indian satellite with instrumentation to detect, locate and characterize electromagnetic signals, such as those transmitted by military radars. The PSLV’s fourth stage will release EMISat, a 961-pound (436-kilogram) spacecraft built for India’s defense forces, in an orbit 465 miles (749 kilometers) above Earth, then maneuver into a lower 313-mile-high (504-kilometer) orbit for the deployment of 28 more satellites, according to information published by the Indian Space Research Organization.

The PSLV is the workhorse rocket for India’s space program, launching several times a year, often with an Indian government satellite and a collection of smaller spacecraft built by organizations and companies in other countries.

A PSLV mission in 2017 set the record for the largest number of satellites ever launched on a single rocket, delivering 104 spacecraft to low Earth orbit for a range of international customers. The upcoming PSLV flight, designated PSLV-C45, will mark India’s second space launch of the year.

The 29 satellites slated to launch on India’s PSLV are enclosed inside the rocket’s payload shroud. Credit: ISRO

Twenty of the secondary payloads set for launch on the PSLV-C45 mission are owned by Planet, a San Francisco-based company which operates more than 100 Earth-imaging satellites. Planet’s next 20 Dove nanosatellites, each about the size of a toaster oven, will join the company’s imaging fleet providing daily views of every location on Earth.

The new batch of Dove CubeSats are part of a group named “Flock 4a” by Planet.

“Flock 4a will join our current constellation of 100+ Doves, replenishing our on-orbit fleet and furthering our daily global monitoring mission,” wrote Mike Safyan, Planet’s vice president of launch, in a post on the company’s website. “However, these Dove satellites aren’t solely for replenishment. They’re equipped with the latest technology – upgrades to our imaging chain to improve image sharpness, radiometric consistency, and spectral precision – and push the boundaries of what our on-orbit Doves are capable of.”

Planet sells its imagery to commercial clients and governments, including U.S. intelligence agencies.

The PSLV launch set for Sunday night (U.S. time) will be India’s first since the country’s military successfully tested an anti-satellite missile Wednesday, destroying an Indian satellite in orbit roughly 175 miles (282 kilometers) above Earth.

India’s test of a satellite kill vehicle shattered the mission’s target, named Microsat-R, into countless fragments. Due to the relatively low altitude of the intercept, most of the material is expected naturally re-enter Earth’s atmosphere within days or weeks, but some debris ejected into higher orbits from the force of the impact could remain in orbit longer.

Officials from several commercial satellite operators, including Planet, condemned the anti-satellite test.

“Space should be used for peaceful purposes, and destroying satellites on orbit severely threatens the long-term stability of the space environment for all space operators,” Planet said in a statement. “Planet urges all space-capable nations to respect our orbital commons.”

Sunday night’s launch will mark the fifth time Planet has put its satellites on an Indian rocket, making Planet one of the Indian space program’s biggest export customers.

Planet books its rides on PSLV missions with Antrix, the commercial arm of ISRO. For Sunday’s launch, Planet arranged for its satellites to ride on the PSLV through Spaceflight, a commercial smallsat launch broker based in Seattle.

The U.S. Air Force’s 18th Space Control Squadron, which detects and catalogs objects in Earth orbit, said in a tweet Friday it is “actively tracking more than 250 pieces of debris associated with (the) Indian ASAT launch” and that the Joint Force Space Component Command is “issuing conjunction notifications to satellite operators as needed to support spaceflight safety.”

Analytical Graphics Inc. modeled the Indian anti-satellite test, and the company’s experts suggested the missile struck the Microsat-R satellite at a relative velocity of nearly 22,000 mph, or 9.8 kilometers per second.

AGI’s simulation predicted the collision created approximately 6,500 debris fragments larger than a pea, about 0.2 inches in diameter. Experts said fewer objects were expected to be large enough to be tracked by the U.S. military space surveillance radars, meaning much of the debris would remain undetected until it fell back into Earth’s atmosphere.

Four Lemur-2 CubeSats owned by Spire Global are also awaiting launch Sunday night, set to join Spire’s fleet of more than 70 active nanosatellites tracking ships and collecting atmospheric data that could one day improve the accuracy of weather prediction models.

The second satellite for Astrocast, a Swiss company aiming to build a network of 64 data relay satellites in low Earth orbit, is also set for launch aboard the PSLV. The shoebox-sized Astrocast 0.2 spacecraft will join Astrocast 0.1, which launched on a SpaceX Falcon 9 rocket in December, to begin demonstrating the company’s concept of using nanosatellites to collect and downlink data from weather buoys, wellhead sensors, pollution monitors and other remote stations.

A Lithuanian company named NanoAvionics has two satellites fastened atop the PSLV.

One the satellites is named BlueWalker 1. It will test unspecified “patented technologies” in space for AST & Science, a U.S.-based smallsat startup company which acquired a controlling interest in NanoAvionics last year, according to company statements.

NanoAvionics announced in February that it was building three low Earth orbit nanosatellites for AST & Science, a list which presumably includes BlueWalker 1. The three nanosatellites “will be used to test a range of experimental payloads for defense and commercial customers, and will include a Q/V-band satellite for test and evaluation,” NanoAvionics said.

NanoAvionics said it took only one month to build BlueWalker 1 and integrate its payload.

“The BlueWalker 1 mission demonstrates how NanoAvionics’ pre-integrated nano-satellite bus enables faster, more responsive approaches for advancing space technology readiness,” said Vytenis Buzas, CEO of NanoAvionics.

The other NanoAvionics satellite launching Sunday, named M6P, hosts two commercial payloads for SpaceWorks Orbital and Lacuna Space, two companies designing communications and tracking networks using tiny satellites as relay nodes, similar to data collection fleet planned by Astrocast.

The BlueWalker 1 and M6P satellites are based on “six-unit” CubeSats, each about the size of a briefcase.

One of Aistech’s CubeSats. Credit: Aistech

The final satellite launching Sunday is AISTECHSAT 3, a smaller two-unit, or 2U, CubeSat for the Spanish company Aistech. The AISTECHSAT 3 nanosatellite is Aistech’s second spacecraft to launch into orbit, and will serve as a pathfinder for the company’s planned network of satellites providing aviation tracking and remote asset management services.

The flight plan for the PSLV’s launch calls for the 145-foot-tall (44-meter) rocket to climb away from the Indian spaceport on Sriharikota Island and initially head toward the southeast.

The PSLV’s solid-fueled core stage and four strap-on boosters will generate more than 1.3 million pounds of thrust at sea level. The four boosters will burn out and jettison around 70 seconds after liftoff, followed by burnout of the first stage motor at T+plus 1 minute, 48 seconds.

A second stage powered by a single Vikas engine will ignite at the same time, generating 180,000 pounds of thrust while burning a mixture of hydrazine and nitrogen tetroxide propellants. The PSLV’s nose cone will jettison in two halves at T+plus 2 minutes, 30 seconds, followed by separation of the second stage at T+plus 4 minutes, 21 seconds.

The rocket’s third stage, also burning solid propellants, will fire nearly two minutes. Then the rocket will begin a coast phase before ignition of the hydrazine-fed fourth stage’s two thrusters at T+plus 8 minutes, 40 seconds.

The fourth stage engines will burn until T+plus 16 minutes, 24 seconds, to place the EMISat spacecraft in its 465-mile-high orbit inclined at 98.4 degrees to the equator. Separation of EMISat is planned at T+plus 17 minutes, 11 seconds.

Two more brief bursts by the fourth stage thrusters, each lasting around 10 seconds, are scheduled at T+plus 1 hour and T+plus 1 hour, 48 minutes. Those maneuvers will lower the rocket’s orbit to an altitude of 313 miles, with an inclination of about 97.5 degrees, setting up for separation of the mission’s 28 other payloads.

The 28 secondary satellites will all be separated from the launcher by T+plus 1 hour, 55 minutes.

Artist’s illustration of the solar arrays mounted on the PSLV’s fourth stage. Credit: ISRO

Further burns by the fourth stage’s attitude control thrusters will steer the rocket into a slightly lower orbit 301 miles (485 kilometers) in altitude, where three experimental payloads mounted to the vehicle will begin their missions.

Indian officials used the fourth stage from the previous PSLV launch in January for long-duration experiments in Earth orbit for the first time. On this mission, engineers added solar panels to the fourth stage for increased longevity.

The fourth stage carries an Automatic Identification System, or AIS, receiver for ISRO to collect messages from ships, an Automatic Packet Repeater System from AMSAT India to assist amateur radio operators in tracking and monitoring position data, and the Advanced Retarding Potential Analyzer for Ionospheric Studies experiment from the Indian Institute of Space Science and Technology for structural and compositional studies of the ionosphere.

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