The sky to get more crowded TECH-ENABLED DEVANGSHU DATTA

Tracking space debris is now an area of commercial interest as satellite launches go up

Space-x recently became the first private operator to ferry astronauts to the International Space Station (ISS). The aerospace company also launches batches of multiple satellites under its Starlink programme. It launched 60 Starlink satellites in May.

This is part of a trend where satellite launches will jump in the next five years. Indian Space Research Organisation estimates that it may participate in over 15,000 launches and many private operators are also in the game along with other agencies.

Satellites are backbone of communications and perform many other tasks as well. The Starlinks will enhance broadband coverage, for example. Locational data, which underpins delivery of pizzas and carnavigation, comes from satellites. They have transformed understanding of weather and climate systems. They are useful in disaster management and used in mapping, calculating forest cover, road-alignment, municipal tax assessments, etc. When it comes to military applications, satellites are a formidable force-multiplier.

But satellites are also a hazard. Astronomers complain they interfere with observations. The new Starlink series has visors to reduce reflection. They also up space. A satellite may continue in orbit once its operational life is over. Or the orbit may decay and it may crash. Or it may collide with another satellite, or a rocket headed for the ISS, or perhaps collide with the ISS itself.

Sir Isaac Newton worked out that there is an ideal orbiting speed at any given altitude. At the ideal speed, a satellite (he calculated it with cannonballs) can move in an orbit around the Earth without further use of power.

Satellites are launched into LowEarth, Medium-earth and High-earth orbits depending on functions. Low Earth (less than 2,000 km above the Earth) is the most crowded with a large number of satellites and defunct satellites. Low Earth orbits have fast-moving satellites, which orbit in 90 minutes or less. Even a tiny object can do a great deal of damage — these move at speeds of 8 km per second.

There are at least 20,000 pieces of space junk, ranging from the large to the tiny orbiting in Low-earth orbits and it’s going to get more crowded. The ISS orbits at 410 km. So it’s a high risk location. Overall, it’s estimated that there at least 20,000 pieces of junk that are tennis-ball-sized or larger (much larger in many cases) and another 500,000 smaller objects out orbiting Earth.

Another crowded belt is the Clarke Belt at 35,000 kms. This is where geostationary and geosynchronous satellites orbit. This altitude is named after scientist and science fiction author, Arthur C Clarke, who conceptualised satellite communications in a 1945 paper. The ideal orbital speed at the Clarke Belt exactly matches the Earth’s rotation speed. A satellite at this altitude is always above the same location (geostationary), or above the same location at the same time everyday (geosynchronous).

Keeping track of everything in space is a daunting task and clearing debris is near-impossible. This is a potential nightmare. Proposed technical solutions include using nets, harpoons, or lasers to remove or destroy junk. Another possibility is inducing a crash once a satellite is past its use-by-date. However, even if junk is removed, operators will want to put new satellites up.

Space situational awareness as tracking space debris is called, is now an area of commercial interest. An American defence contractor, Analytical Graphics, opened a Commercial Space Operations Center in March 2019 to track both active satellites and space junk. Lockheed Martin has set up a space-debris tracking site in Western Australia.

A new paper (https://www.pna s.org/content/117/23/12756 Orbital-use fees could more than quadruple the value of the space industry) proposes an economic solution that factors in costs and sets internationally-agreed fees for every orbiting satellite.

This uses a model similar to carbon taxes. These fees could be tradeable tokens like carbon credits and they would be calculated according to risks caused by a given satellite. The fee for each satellite would be calculated to reflect the cost to industry of putting an equivalent satellite into orbit, including estimated costs of collision risk, and space debris production. These fees would rise over time, with the paper calculating a CAGR of 14 per cent for an averaged fee of $235,000 per satelliteyear by 2040.

All spacegoing nations would have to agree to such a proposal which is hard to envisage but stranger things have happened. About 12 nations currently launch satellites and some 35 own satellites. Given orbital-use fees, the longterm value of the satellite industry would increase from around $600 billion (without fees) to around $3 trillion, the paper claims. The increase in value comes from reducing collision risks. It will be interesting to see if some variation of this plan is ever adopted.