ISRO has initiated an early warning system called Project NETRA (Network for space object Tracking and Analysis), that would help detect space hazards to Indian satellites.
About the Project NETRA (Network for space object Tracking and Analysis)
Space situational analysis(SSA)
Project is expected to give India its own capability in space situational awareness (SSA), something that other space powers already have.
- The SSA is used to predict threats from debris to Indian satellites. It also serves as a warning system against missiles or a space attack against India.
- Our SSA will first be for low-earth orbits or LEO which have remote-sensing spacecraft.
It can spot, track and catalogue objects as small as 10 cm, up to a range of 3,400 km and equal to a space orbit of around 2,000 km.
The new SSA centre floated by ISRO would consolidate debris tracking activities, currently spread over ISRO centres across India.
Eventual goal for NETRA would be to capture the geostationary orbit.
ISRO also plans on putting up a number of observational facilities, including connected radars, telescopes, data processing units and a control centre.
A high-precision, long-range telescope in Leh and a radar in the North East are also being planned.
Along with them, ISRO will also use the Multi-Object Tracking Radar (MOTR) put up at the Satish Dhawan Space Centre in Sriharikota, and the telescopes at Ponmudi and Mount Abu to get a broad SSA picture.
By establishing an observation system of its own, ISRO will become a part of the global network and can access precise data.
Background:Problem of Space Junk
- Space junk is an ever-growing problem with more than 7,500 tonnes of redundant hardware now thought to be circling the Earth. Ranging from old rocket bodies and defunct spacecraft through to screws and even flecks of paint – this material poses a collision hazard to operational missions.
- The rising population of space debris increases the potential danger to all space vehicles, but especially to the International Space Station (ISS), space shuttles, satellites and other spacecraft.
- Currently there are 15 functional Indian communication satellites in the geostationary orbit of 36,000 km including 13 remote sensing satellites in LEO of up to 2,000 km and eight navigation satellites in medium earth orbits.
- Even now ISRO does collision avoidance manoeuvres on its satellites. To do that, it depends on data from NORAD and others available in the public domain. But, it doesn't get accurate (or comprehensive) information.
- The North American Aerospace Defense Command (NORAD)
- It is an initiative by the US and Canada which helps in sharing selective debris data with many countries.
- It provides aerospace warning, air sovereignty, and protection.
Types of satellite orbits
- As satellites in geostationary orbit continuously cover a large portion of the Earth, this makes it an ideal orbit for telecommunications or for monitoring continent-wide weather patterns and environmental conditions.
- It also decreases costs as ground stations do not need to track the satellite. A constellation of three equally spaced satellites can provide full coverage of the Earth, except for the polar regions.
- These satellites appear nearly stationary in the sky as seen by a ground-based observer.
Geostationary transfer orbit
- This is an elliptical Earth orbit used to transfer a spacecraft from a low altitude orbit or flight trajectory to geostationary orbit. The apogee is 36,000 km.
- When a spacecraft reaches this point, its apogee kick motor is fired to inject it into geostationary orbit.
Low Earth orbits
- A low Earth orbit is normally at an altitude of less than 1000 km and could be as low as 160 km above the Earth.
- Satellites in this circular orbit travel at a speed of around 7.8 km per second. At this speed, a satellite takes approximately 90 minutes to circle the Earth.
- In general, these orbits are used for remote sensing, military purposes and for human spaceflight as they offer close proximity to the Earth’s surface for imaging and the short orbital periods allow for rapid revisits.
- The International Space Station is in low Earth orbit.
Medium low Earth orbit
- This orbit takes place at an altitude of around 1000 km and is particularly suited for constellations of satellites mainly used for telecommunications.
- A satellite in this orbit travels at approximately 7.3 km per second.
- Polar orbits pass over the Earth’s polar regions from north to south.
- These orbits mainly take place at low altitudes of between 200 to 1000 km.
- Satellites in polar orbit look down on the Earth’s entire surface and can pass over the North and South Poles several times a day.
- Polar orbits are used for reconnaissance and Earth observation.
- If a satellite is in polar orbit at an altitude of 800 km, it will be travelling at a speed of approximately 7.5 km per second.
Sun synchronous orbits
- These are polar orbits which are synchronous with the Sun.
- A satellite in a sun synchronous orbit would usually be at an altitude of between 600 to 800 km.
- These orbits are used for Earth observation, solar study, weather forecasting and reconnaissance, as ground observation is improved if the surface is always illuminated by the Sun at the same angle when viewed from the satellite.
DRDO NETRA: A Project For Internet Surveillance
- NETRA (NEtwork TRaffic Analysis) is a software network developed by India's Centre for Artificial Intelligence and Robotics (CAIR), a Defence Research and Development Organisation (DRDO) laboratory.
- It is used by the Intelligence Bureau, India's domestic intelligence agency, and the Research and Analysis Wing (RAW), the country's external intelligence agency to intercept and analyse internet traffic using predefined filters.