National Space Day: The road in space travelled by ISRO

The Indian government has designated August 23 as National Space Day to commemorate the successful soft landing of the Chandrayaan-3 lander, Vikram, and rover, Pragyan. Since its inception in 1969, the Indian Space Research Organisation (ISRO) has added many feathers to its cap.

ISRO's inception

Jawaharlal Nehru, India's first prime minister, considered science and technology crucial to ensuring a bright future and the well-being of the newly independent nation. He actively promoted research and development in advanced and frontier areas of science and technology at the time. Nudged by Homi Bhabha, and with the support of Nehru, 'space research and the peaceful applications of outer space' was designated as a critical topic and placed under the control of the Department of Atomic Energy. Physical Research Laboratory (PRL) in Ahmedabad, established by Vikram Sarabhai, was designated as the nodal centre for space science research and development, and he was appointed to the Atomic Energy Commission's board.

The Indian National Committee for Space Research (INCOSPAR) was founded in 1962 by Vikram Sarabhai with the backing of Nehru. This group, which preceded the founding of ISRO, was essential in setting the groundwork for India's space research and exploration efforts. The same year, work on the Thumba Equatorial Rocket Launching Station (TERLS) near Thiruvananthapuram commenced. The inaugural launch occurred on November 21, 1963, from this launch pad.

At first, the rockets were imported from the Soviet Union and France. However, by 1965, indigenous-sounding rockets were developed. With the space programme advancing, ISRO was founded in November 1969. In 1972, the government established a space commission akin to the Atomic Energy Commission, as well as a separate agency called the Department of Space (DOS). ISRO was incorporated into this newly formed department.

Since its creation in 1969, ISRO has undertaken 127 launches and placed 97 Indian payloads into space, including 18 conceived and developed by students and educational institutions. ISRO has launched a staggering 432 satellites from 34 countries, demonstrating India's expanding presence in the international space market. ISRO's assistance in launching vehicles designed by Indian startups Agnikul Cosmos and Skyroot Aerospace highlights the organization's substantial contributions to the emergence of national aerospace startups.

Currently, 24 satellites are in low earth orbit (LEO), plus 30 in geosynchronous orbit. In addition, three Indian deep space missions are operational: the Chandrayaan-2 Orbiter, Aditya-L1, and the Propulsion Module of Chandrayaan-3.

Space technology includes a) a variety of launch vehicles, b) the design and development of satellites for communications, remote sensing, weather studies, and navigation applications, and c) space research, such as space telescopes and travel to the Moon and other planets. ISRO has excelled in all of these areas.

Launch vehicles

ISRO's first launch vehicles were sounding rockets. These rockets launch a payload of scientific devices to research the upper atmosphere or outer space. The rocket injects the payload in a parabolic trajectory that lasts 5 to 20 minutes.

The Rohini-75, or RH-75, is the first sounding rocket produced entirely by indigenous efforts. The name '75' denotes that the missile had a diameter of 75 mm. This was followed by RH-100 and RH-125 rockets. These solid-fuel rockets served as the foundation for ISRO’s space technology experience, including solid fuel, rocket engines, flight control and navigation, tracking, and telemetry. ISRO currently has three sounding rockets in its fleet; the RH-200, which can lift a 10 kg payload to a height of 80 km; the RH 300-Mk-II, which can lift a 60 kg payload to a height of 160 km; and the RH 560 MKII, which can lift a 100 kg payload to 470 km. While RH 200 can be launched from Thumba, the others are launched only from the Sriharikota launch pad.

After learning how to manufacture and launch rockets, ISRO progressed to a more advanced version capable of placing payloads into orbit. Satellite Launch Vehicle-3 (SLV-3) was created in the early 1980s as a solid, four-stage rocket capable of launching a 40 kg payload into low-Earth orbit. This was followed by the Augmented Satellite Launch Vehicle (ASLV) in the late 1980s. ASLV, a five-stage, all-solid propellant rocket, can launch a 150 kg payload into low-Earth orbit. Both these launch vehicles are retired now.

The third-generation Polar Satellite Launch Vehicle (PSLV) was India's first rocket to employ liquid fuel. The first and third stages are solid, while the second and fourth stages use liquid fuel. This four-stage rocket, known as the 'workhorse of ISRO', can place a 1,750 kg payload in low earth orbit. It can also launch a 1400 kg payload into a geostationary transfer orbit (GTO), which can be transported to a geosynchronous or geostationary orbit.

Since its first launch on September 20, 1993, ISRO has had a remarkable track record, with 57 successful launches, one partial success, and only two failures through August 2024. This reliability has positioned ISRO's PSLV as some of the most trustworthy and dependable in the world, inspiring confidence in the global space community.

ISRO designed the fourth-generation Geosynchronous Satellite Launch Vehicle (GSLV) to accommodate heavier payloads, like communication satellites and spacecraft for planetary missions. This three-stage launch vehicle employed solid fuel in the first stage, liquid fuel in the second, and more advanced cryogenic fuel in the third. The first two stages launch the payload into space. The cryogenic stage assists in putting the satellite into a geo-transfer orbit, which allows it to be placed in a geosynchronous orbit. These launch vehicles could place a payload of 6,000 kg in low earth orbit and 2,500 kg in GTO.

Initially, cryogenic engines were imported from Russia. Five launches were carried out utilizing Russian engines, two successful, two partial successes, and one disaster. However, the Americans persuaded Russia not to sell the engines to India. This put ISRO in an impasse. This became a blessing in disguise. Unfazed, the cryogenic stage was wholly built by Indian researchers, and the engine's first launch took place in January 2014. ISRO branded these as GSLV Mk II to distinguish them; all six launches have been successful so far.

ISRO designed a high-thrust cryogenic upper stage (C25) to boost payload capacity and built the GSLVmk3, which was later renamed LVM3. The media frequently refers to this as the ISRO's 'Baahubali'. This launch vehicle consists of two solid strap-on motors in the first stage, a liquid core stage in the second, and a high thrust cryogenic upper stage (C25) in the third, allowing it to launch 4000 kg of spacecraft into GTO (Geosynchronous Transfer Orbit) and 0 kg cargo into low-Earth orbit. This vehicle can transfer 3000 kilograms to the Moon using translunar injection. There have been seven launches, including Chandrayaan 2 and 3, all of which have succeeded.

Human-rated LVM3 (HLVM3) is a type of LVM3 with a Crew Escape System (CES) currently under development for the Gaganyaan mission, which aims to send Indians into space.

Meanwhile, the space industry saw a sea change. A satellite weighing 10 to 20 tons placed in geostationary orbit with a lifespan of 20 to 30 years was no longer desirable. Science and technology advanced so rapidly that the ground segment often used significantly more complex electronics than the payload in the space. The space industry devised a radical answer. Use low-earth orbit and a train of low-cost, tiny microsatellites with a one to two-year lifespan that can be replaced once the electronics expire. Thus, the space sector's needs have shifted from large payloads to be deployed in faraway geostationary orbits to small, micro, and nanosatellites in nearby low-earth orbits.

Given the expanding market for mini, micro, and nanosatellites, ISRO immediately designed a three-stage, all-solid fuel launch vehicle known as the mini Satellite Launch Vehicle (SSLV). SLV3's expertise aided ISRO's development of this technology. The first of the three launches was unsuccessful, while the following two were successful. ISRO also quickly established a second spaceport in Kulasekarapattinam to fulfil the demands of the SSLV launch, in addition to the one in Sriharikota.

Satellites

Communication satellites have been one of ISRO's primary priority areas. APPLE, a satellite with a single transponder, was designed, produced, and launched in 1981. ISRO created the Indian National Satellite System (INSAT), a geostationary satellite system designed to address a variety of needs, including telecommunications, television, meteorology, and search and rescue missions. From a single transponder in the first endeavour, the most recent GSAT 24 contains 48 transponders spanning three frequency bands: 24 in the C band, 12 in the Extended-C band, and 12 in the Ku-band.

The first effort, INSAT-1A, launched on April 10, 1982, failed. The first operational INSAT was INSAT-1B, put into orbit by the Space Shuttle on August 30, 1983. INSAT is currently one of the largest communication satellite networks in geostationary orbit, with 200 transponders in the C, Extended C, and Ku bands used for telecommunications, television broadcasting, satellite news gathering, societal applications, weather forecasting, disaster warning, and search and rescue.

Since 2001, ISRO has expanded the INSAT program with GSAT, a series of indigenously developed communications geosynchronous satellites for digital music, data, and video broadcasting. CMS, a new series of communication satellites, is being developed, with the launch of CMS-01 in December 2020. To date, 49 communication satellites have been launched.

Another area of focus for ISRO has been remote sensing and Earth observations, such as weather monitoring. Since the launch of Bhaskara-I on June 7, 1979, ISRO has launched 45 remote sensing and Earth observation satellites that have helped in surveying and planning agriculture, water resources, urban planning, rural development, mineral prospecting, the environment, forestry, ocean resources, and disaster management. The multi-purpose Indian Remote Sensing (IRS) satellite series have been replaced by second-generation specific purpose satellite series such as CARTOSAT, RISAT OCEANSAT, RESOURCES, and, most recently, Earth Observation Satellites (EOS).

ISRO has launched nine satellites for the Indian Regional Navigation Satellite System (IRNSS), eight of which are operational. This helps provide indigenous space-based navigation support to strategic sectors.

ISRO launched AstroSat, one of its first space observatories. This space telescope, launched into low Earth orbit in 2015, is still operational. The Mars Orbiter project was ISRO's first interplanetary mission, while Chandrayaan-1 was the first lunar orbiter mission. The significant endeavours of ISRO in space missions include Chandrayaan-2 and Chandrayaan-3, ambitious missions to soft-land on the Moon, and Aditya-L1, dedicated to the study of the Sun.

The first uncrewed test flight of India's human-rated rocket for its first human space mission, 'Gaganyaan', is set for December 2024. The ISRO's Sukrayaan mission aims to reach Venus. MOM-2 to study Mars, Chandrayaan-4 with an ambitious plan for a sample return mission that would bring a small quantity of lunar dirt and rocks back to Earth, and the Lunar Polar Explorer mission with Japan are some of the ambitious future plans that are being developed.

ISRO is also planning an Indian space station that will allow three to four astronauts to reside and conduct research for 10-20 days in space.

Key milestones

• 1962: Indian National Committee for Space Research (INCOSPAR) was instituted
  
• ISRO was established in August 1969.
• The first sounding rocket launch from Thumba occurred on November 21, 1963.
• On November 20, 1967, the indigenously developed RH-75 (ROHINI-75) sounding rocket was launched.
• On April 19, 1975, Aryabatta-1, an indigenously manufactured satellite, was launched using a Soviet launch vehicle.
• On May 31, 1981, an indigenously built 35 kg Earth observation satellite was launched by an indigenously created SLV-3D1 launch vehicle.
• On May 20, 1992, the next-generation launch vehicle ASLV launched SROSS satellite C2, which carried out gamma-ray burst (GRB) and retarded potential analyzer (RPA) experiments.
• On May 21, 1996, the third-generation vehicle PSLV-D3 launched the IRS-P3 remote sensing satellite into space.
• On April 18, 2001, the fourth generation GSLV-D1 launched a communication satellite into GTO, using a cryogenic upper stage powered by Soviet cryogenic engines.
• On January 5, 2014, GSLV MkII, with the Indigenous Cryo Stage, launched GSAT-14 into GTO orbit.
• On October 22, 2008, a lunar orbiter was launched as part of the Chandrayaan-1 mission. On November 14, 2008, a lunar impact probe disconnected from the orbiter and deliberately crashed on the lunar's surface. The expedition discovered clear evidence of water on the Moon.
• On November 5, 2013, the Mars Orbiter Mission, also known as Mangalyaan, was launched. It entered lunar orbit on September 24, 2014, and remained operational until October 2, 2022. It helped us understand plant-wide sandstorms, the degassing of Mars' atmosphere, and many other scientific findings.
• A critical Crew Module Atmospheric Re-entry Experiment (CARE) for the Gaganyaan mission was carried out on December 18, 2014, using the GSLV Mk3/LVM3.
• On September 28, 2015, India launched its first space telescope, ASTROSAT, into orbit.
• June 5, 2017: Upgraded GLSV Mk3, renamed LVM3, placed GSAT-19 in GTO.
• On June 12, 2019, the first test flight of an indigenously developed unmanned scramjet was conducted.
• July 22, 2019—The Chandrayaan-2 mission to soft land on the Moon was launched. The orbiter reached the lunar orbit, but the lander failed to soft land. The mission was partially successful.
• On February 10, 2023, the SSLV D2 launched the AzadiSAT, EOS-07, and Janus-1 satellites into low Earth orbit.
• July 14, 2023—Chandrayaan 3 was launched with the goal of soft landing on the lunar surface. The lander arrived on the Moon's surface on August 23, 2023. The lander and rover operated for 14 days, one lunar day.
• September 2, 2023 - Aditya L1, a space satellite for studying the Sun, is launched. On January 6, 2024, the vessel arrived at the L1 point and began observing and studying the Sun.