IRS-1A: India’s Initiation to Distant Sensing

It is the yr 1975. India simply launched its first satellite tv for pc, Aryabhata. The satellite tv for pc operated just for a couple of months, however ISRO realized so much throughout the journey for reaching this dream. The Aryabhata mission’s success resulted in new applications for communication satellites (APPLE/INSAT) and distant sensing satellites. Allow us to be taught in regards to the first operational satellite tv for pc totally designed and developed by ISRO, IRS-1A: India’s Initiation to Distant Sensing.

Background: A legacy of Aryabhata, Bhaskara and APPLE

Over the subsequent few years, to proceed Vikram Sarabhai‘s imaginative and prescient, the company constructed two extra experimental satellites referred to as Bhaskara 1 and Bhaskara 2. Whereas Aryabhata was a scientific satellite tv for pc, Bhaskara(s) have been distant sensing satellites in some sense. They’d digital camera payloads however lacked the strict parameters of operational distant sensing satellites like a completely steady satellite tv for pc. The Bhaskara satellites, due to this fact, have been a step ahead in the correct route. ISRO examined some key applied sciences whereas leaving out some superior ones.

APPLE Satellite Testing in 1981
APPLE Satellite tv for pc Testing in 1981 | Credit: ISRO

On the communication satellites entrance, APPLE once more was an experimental satellite tv for pc, whereas the primary operational satellites INSAT-1 sequence have been procured. Due to this fact, when the design and improvement of the primary operational satellite tv for pc, IRS-1A, began, ISRO ventured into unknown territory on many fronts: management methods, deployable photo voltaic panels, floor station, high quality management protocols and knowledge utilisation, to call a couple of.

The Bhaskara satellites launched in 1979 and 1981, respectively. Across the similar time, the thought of an operational distant sensing satellite tv for pc was going round in ISRO. The Nationwide Pure Sources Monitoring and Administration System (NNRMS) of Govt of India thought-about important areas of utility of satellite-based distant sensing knowledge as

  1. Agriculture, the place the extent of crops and their yields have been required to be monitored over the rising seasons,

  2. Monitoring of the several types of land/land use,

  3. Monitoring of water assets,

  4. Monitoring of drought and floods,

  5. Monitoring of the forestry within the nation, and

  6. Geological functions like mineral prospecting.

The agricultural functions gained precedence over different areas. In India, a typical agricultural area had a 30 m size. Due to this fact, a 36 m decision payload was chosen for the satellite tv for pc. Different functions might work with a course decision which resulted within the inclusion of a separate 72 m decision payload.

With these payloads finalised, the House Fee submitted a proposal to the Authorities of India, giving full particulars of the mission. ISRO included an inventory of latest applied sciences to be developed, specs of satellite tv for pc and floor section, finances, import necessities, schedule and venture administration facets within the report. Lastly, the GOI authorized the IRS-1A satellite tv for pc in 1981.

IRS-1A Growth: Realising new applied sciences

The imaging methods, together with nice resolutions, require multispectral knowledge. Completely different frequency vary channels assist classify numerous options resembling water our bodies, inexperienced covers, and building. Due to this fact, ISRO included 4 bands (blue, inexperienced, crimson, and infrared) in every of the 2 cameras.

Subsequent got here the choice of orbit choice. To watch the expansion of crops in a season, a repetitiveness of twenty-two days was set. This requirement meant ISRO chosen a 900 km Polar Solar-synchronous orbit. Due to this fact, two LISS (Linear Self Scanning Scanner) payloads have been developed for the IRS-1A satellite tv for pc.

Illustration of IRS-1A satellite
Illustration of IRS-1A satellite tv for pc | Credit: ISRO

The satellite tv for pc wanted a number of new applied sciences to assist the imaging system.

  • A 3-axis stabilised satellite tv for pc with cameras mounted appropriately to take photos of the Earth’s floor with pointing accuracies of ± 0.3 levels about pitch and roll axis and ± 0.4 levels in regards to the yaw axis,

  • Energy system to supply the required conditioned energy,

  • Telemetry, Monitoring and Command (TT&C) system working in S-band,

  • Information dealing with and radiofrequency transmit methods for transmitting the digital camera knowledge, and

  • The mechanical system consisting of a construction, thermal management and photo voltaic panel deployment mechanism.

Mechanical Subsystem

An aluminium honeycomb construction was realised to assist completely different devices. Particular concerns meant that the satellite tv for pc bus was appropriate with completely different launch automobiles, together with the upcoming PSLV. A passive (no electrical energy wanted) thermal system developed the place the cameras remained at the usual room temperature.

All prior ISRO satellites had everlasting mounted photo voltaic panels. An imaging satellite tv for pc like IRS-1A wants excessive energy. Due to this fact deployable photo voltaic panels are required. The staff developed a mechanism that underwent greater than 50 checks, together with zero-gravity testing.

Management Sub-System

Being the primary three-axis stabilised satellite tv for pc, IRS-1A wanted many new management methods. Angle sensors, dynamically tuned gyroscope, response wheels and mono-propellant based mostly propulsion system have been developed. Digital microprocessors was a brand new expertise on the planet. This lead ISRO to make use of a hardware-based management system with a secure mode inbuilt.

Communication Subsystem

The imaging digital camera knowledge was beamed again to Earth in real-time. There was no recorder onboard. This meant that the payload knowledge wanted an Earth-pointing antenna whereas the Telemetry and Telecommand antenna needed to be omnidirectional.

Energy Subsystem

ISRO imported Photo voltaic cells and Ni-Cd Batteries. An influence system examined and certified for house was designed round these imported parts. The staff developed energy conditioners to transform uncooked energy into regulated energy voltage.

IRS-1A additionally paved the trail for managerial facets

By that point, ISRO had expanded so much. There have been a number of centres of the house company unfold all through the nation. IRS-1A grew to become one of many first inter-departmental efforts. ISRO satellite tv for pc centre (URSC) lead the venture and coordinated with all different centres. The Mission Administration Council (PMC) chaired by Dr UR Rao and a Mission Administration Board (PMB) chaired by Dr Okay Kasturirangan have been shaped at URSC to information the venture and conduct higher-level mission evaluation.

The House Functions Centre, Ahmedabad, developed the imaging system and even the info merchandise to analyse the distant sensing knowledge. Groups developed the management methods and photo voltaic panel deployment at ISRO Inertial Techniques Unit (IISU), VSSC. Liquid Propulsion Techniques Centre (LPSC), Bangalore, developed the propulsive system wanted to regulate the satellite tv for pc.

Whereas this inter-departmental effort was present process, ISRO shaped a brand new centre. Till now, ISRO utilised a floor station on the Sriharikota Launch Vary as a command station for its satellites. ISRO Telemetry Monitoring and Command Community (ISTRAC) was developed as a Management Centre for IRS-1A and all upcoming Indian Distant Sensing (IRS) satellites. Bearslake station in Moscow, Fairbanks station in Alaska, Weilheim station in Germany, Malindi station positioned in Kenya, operated by ESA, have been the stations recognized for the community.

The Nationwide Distant Sensing Company, Hyderabad (now NRSC), was already receiving payload knowledge from NASA Landsat and French SPOT satellites. New floor methods developed to obtain IRS-1A satellite tv for pc knowledge.

IRS-1A Satellite
IRS-1A satellite tv for pc | Credit: VSSC

High quality Assurance and Testing

The inter-departmental effort and a number of industries concerned meant uniform high quality assurance norms was wanted throughout all centres. ISRO constituted a Product Assurance Board which catered to reliability apportionment of the satellite tv for pc. The groups required to get each element checked with the board by way of guidelines paperwork.

Each subsystem of the satellite tv for pc was completely examined by way of newly developed testing setups. The groups even developed a number of fashions resembling a structural mannequin for vibration testing, qualification mannequin for testing and last flight mannequin. ISRO first used this a number of mannequin philosophy for the IRS-1A mission.

Launch and Operations

ISRO’s Polar Satellite tv for pc Launch Automobile (PSLV) was nonetheless underneath improvement. This restricted the company to make use of a overseas launcher for the satellite tv for pc. After the Soviets helped India launch the primary satellite tv for pc, Aryabhata, ISRO determined to strategy them once more. Soviet Union agreed to launch IRS-1A onboard a VOSTOK rocket at a “affordable price ticket”.

There have been a number of visits by Soviet Scientists to help ISRO to design a appropriate satellite tv for pc. Even ISRO scientists AD Dharma S Kalyana Raman visited Baikonur Cosmodrome. Just a few days earlier than launch, the satellite tv for pc was flown onboard an Aeroloft IL-76 cargo plane on twenty fourth January 1988.

After conducting some extra checks, resembling photo voltaic panel deployment and gasoline loading, the satellite tv for pc was built-in with the launch car. IRS-1A launched at 12:13 IST on seventeenth March 1988.

The photo voltaic panels deployed with none hiccups after a couple of minutes. On 18th March, the satellite tv for pc had acquired stabilisation, and the LISS-1 was switched on. Just a few extra days later, the LISS-2 payload began sending photos as properly. Inside three weeks, the satellite tv for pc was operationalised and knowledge made obtainable to the scientists.

UR Rao had turn into the ISRO chairman by then. He constituted the Antrix Company to promote the IRS sequence knowledge internationally commercially. Therefore, the industrial arm of ISRO was shaped. IRS-1A labored for nearly 9 years, far more than its three-year design life.

IRS sequence: The Highway Forward

IRS-1A had a paved path for quite a few services and procedures at ISRO. Using on the primary distant sensing satellite tv for pc’s success, ISRO designed IRS-1B/C/D satellites within the coming years. In 1993, PSLV grew to become operational, and India now launched the satellites on our personal launch car. The Indian Distant Sensing community is without doubt one of the largest nationally operated all over the world. IRS programme has developed to incorporate many satellites resembling Resourcesat, Cartosat and the newest EOS sequence satellites.


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