NASA rescued a satellite near Mars. Saving Earth's satellites is harder.
On March 6, NASA鈥檚 MAVEN Mars orbiter with the Red Planet鈥檚 moon Phobos. At first, computer models showed the two satellites missing each other by just seven seconds.
Mission controllers decided that was too great a risk for the $671 million spacecraft, whose name stands for Mars Atmosphere and Volatile EvolutioN. So, on Tuesday, enough to increase its velocity by 0.4 meters per second. Controllers say that small correction will yield a safe 2.5 minutes between MAVEN and Phobos on the 6th.
Maneuvers like this will likely become more common as traffic to the Red Planet increases. They鈥檙e already commonplace in Earth orbit, says space policy expert Brian Weeden. 鈥淢ost objects on a collision course in space move too fast for the human eye to see and .... the collision will happen much faster than any human could possibly react to,鈥�
Instead, when orbital models predict a close pass, 鈥渁 warning is provided to the satellite operator or operators involved along with the probability of collision,鈥� he explained. 鈥淚t is currently up to each operator to determine their own tolerance for risk and use that as a basis for determining whether or not to maneuver the satellite to change its trajectory and avoid the close approach.鈥�
Satellite operators can direct spacecraft in Earth orbit to carry out these maneuvers in seconds, compared with 13 minutes for Mars. But the sheer number of satellites now orbiting Earth may make preventing collisions over our own heads more difficult 鈥� and more important.
There are currently orbiting Mars, SpaceFlight Insider reports. They鈥檝e already proven themselves adept at evasive maneuvers like MAVEN鈥檚 on Tuesday, or a 鈥溾�� one performed during a 2014 comet flyby. By contrast, Earth can currently claim more than 1,400 operational man-made satellites, .
That number鈥檚 growing fast, thanks to the development of 鈥溾�� that can measure as small as 10x10x10 cm, at prices that universities and startup firms can afford. India sent 103 CubeSats 鈥� plus a larger conventional satellite 鈥撀犅爄nto orbit last month on a single rocket.
Dr. Weeden, who serves as the director of Program Planning at the Secure World Foundation,聽which works to promote sustainaibility in space, sees trouble in this trend. Many of these new satellites, he told Congress, have no propulsion system, are difficult to track because of their size, and are 鈥渄eveloped and operated by new space actors who may not have the experience to do so safely or responsibly.鈥�
鈥淭his means that ... when involved in a close approach with another space object they are for all intents and purposes just another piece of space debris,鈥� he said.
. Hugh Lewis, a space debris expert from the University of Southampton, has counted more than 360,000 close encounters involving the satellites since 2005. G. Madhavan Nair, former chairman of the Indian Space Research Organization, has even raised doubts about whether his country should continue to launch CubeSats, warning that India could be liable for damages from a future collision with a foreign satellite.
To reduce the likelihood of these collisions, the Secure World Foundation and other 鈥渟pace sustainability鈥� advocates want to strengthen spacecraft regulations, expand monitoring of Earth鈥檚 orbital neighborhood, and increase coordination among spacefaring nations. More ambitious schemes 鈥� like deploying a 鈥渟pace whip鈥� to capture debris 鈥� haven鈥檛 yet borne fruit.
Some scientists worry that, if left unchecked, increased 鈥渟pace junk鈥� could lead to the , in which a chain reaction of collisions leaves Earth surrounded with a belt of debris. Already, 鈥� and sent a fictional astronaut played by George Clooney to an untimely death in the 2013 movie Gravity.
Dr. Weeder doesn鈥檛 see 鈥渁n infinite growth in the debris population鈥� coming to pass. But a future with more collisions and 鈥渟pace junk,鈥� he told Congress, could easily result in 鈥渋ncreased operating costs to try to detect and avoid potential collisions.鈥�
鈥淭hese rising costs will likely hinder commercial development of space and will place additional pressure on government budgets, potentially resulting in the loss of some of the benefits we currently derive from space.鈥�
