A Chinese military satellite, Yunhai 1-02, has become the latest victim of orbital debris. Yunhai was launched and began functioning in late 2019 and suddenly went silent in March 2021. At first it was believed that Yunhai broke up because of an internal explosion or collision. It was later confirmed that Yunhai was hit on March 18th by a fragment from a 1996 Russian satellite launch in which several large fragments from the final stage of the SLV (Satellite Launch Vehicle) remained in orbit rather than falling back to earth and burning up as they entered the atmosphere. That Russian ELINT (electronic intelligence collection) satellite, Tselina-2, weighed 3.2 tons and used batteries and solar arrays to maintain power and operate for at least a year in an orbit 850 kilometers above earth. Yunhai was not destroyed by the collision but was seriously damaged. The collision generated several large pieces of new debris. The Yunhai 1-02 is still emitting signals but is believed to be useless for its intended function.
The piece of space junk that hit Yunhai 1-02 was estimated to be 10-50 cm (4-20 inches) wide and had not been detected earlier and tracked, as had five other fragments from the 1996 SLV incident. Other fragments were suspected but could not be detected and tracked. When a satellite is damaged or destroyed by an untracked fragment it is often possible to determine which identified batch (swarm) of debris it came from and this was apparently the case with debris from the 1996 SLV.
Since the 1990s there have been improvements in preventing dangerous fragments from satellite launchers and satellites that have ceased to be useful. This is in addition to equipping satellites with a deorbiting system that will reliably move it to a lower orbit so it will enter the atmosphere and burn up.
Collisions like this confirm the growing need to find, track and report orbital debris as well as satellites. That effort has been going on for decades and generates more and more international cooperation. For a long time the major satellite producers (the U.S., China and Russia) did not reveal all they know. Despite that there is a growing need for as complete a debris database as possible to be maintained and made public. For example, in early 2013 Russia reported that one of its satellites was hit and damaged by debris from a Chinese satellite that China had destroyed in a 2007 anti-satellite weapon test. This is only the second time that an active (still operational) satellite was hit by orbital debris. The last time was in 2009 when an American satellite was hit by a dead Russian satellite. Since then, owners of active satellites have paid more attention to where all the space junk (debris) is up there, and it is more common for active satellites to move out of the way of oncoming concentrations of debris. This consumes precious fuel, which is normally used to maintain a low flying satellite in the proper orbit. When the fuel is gone, so is the ability to move and the usefulness of the satellite.
The loss of Yunhai 1-02 is the first since the 2009 loss of an American Iridium satellite, which supplies satellite phone service and was at an altitude of about 770 kilometers over central Russia. The Iridium satellite was hit by a dead Russian communications satellite, the one-ton Cosmos 2251 which was equipped with a nuclear power supply. Launched in 1993, the Russian bird could not be moved, nor could the Iridium which, while active, was not equipped with thrusters for movement. The Iridium satellite was one of sixty, so satellite phone services were not interrupted because of the system’s spare capacity. The collision turned the two satellites into 600 bits of trackable, and very dangerous, debris.
The first such satellite loss to debris was in 1991 when a dead satellite ran into debris from another and created more debris. There have been two deliberate collisions since then. In 2007, China launched a "killsat" that maneuvered into the path of a dead Chinese weather satellite and destroyed it. In 2008, the U.S. Navy used one of its Aegis equipped warships to destroy a malfunctioning U.S. spy satellite with an anti-missile missile. Russia and China have since called for such U.S. activity to be outlawed. These three counties are responsible for putting the majority of satellites into orbit and generating most of the orbital debris up there.
Since the late 1950s, humans have been putting objects into orbit and there is a rapidly growing collection of junk up there. Currently, there are about 130 million pieces of debris smaller than ten mm (millimeters) or .4 inches) in orbit. These are large, and fast, enough to damage operational space satellites and even kill astronauts in space suits. Most of this tiny debris is no larger than a bit of flaked paint, and other objects the size of a grain of sand or small pebble. Even the tiniest of items, like some paint chips or frozen drop of rocket fuel, moving at high speed, create visible, if not very damaging, evidence of collisions. Occupied spacecraft or space stations alert inhabitants when such tiny objects hit the hull or other equipment, like solar arrays. Too many of these encounters with microscopic objects can cause real damage while weakening the satellite or space station in question.
Over 900,000 objects 10 mm (.4 inch) in size have been identified and these are more dangerous. The smallest of these can disable a satellite, or damage a spacecraft, mainly because these objects collide at very high speed (9-10 times faster than a bullet) when the two objects are coming from different directions.
There are nearly 35,000 objects 10 centimeters (4 inches) or larger in LEO (low earth orbit). All of these can do some catastrophic damage to satellites or spacecraft. The millions of objects smaller than 10mm are responsible for many satellites failing early because of cumulative damage from getting hit by several of these micro-objects. There are over 2,500 commercial and military satellites up there, most of them still operational and a growing number of the nano (very small) sats. Also called cubesats, they take advantage of smaller and lighter components and the ability of SLVs to deliver over a hundred nanosats into orbit at one time.
There are a growing number of dead satellites in LEO with orbits degrading so slowly that it may be decades before they get low enough to be pulled into the atmosphere and burn up. The nanosats are in the lowest LEO orbits and not capable of moving themselves lower when the useful life ends. Instead, the nanosats are low enough to more quickly drift earthwards and into the atmosphere at about a hundred kilometers above earth where gravity and atmospheric friction begins burning them up.
Because of increased cooperation and openness by the major space satellite producing nations, most of the details of how the Yunhai 1-02 debris damage was caused came from the recently created U.S. Space Force, which has several components that monitor orbit space and track debris. Russia and China have also become more forthcoming about these incidents and space debris in general. In mid- 2018 Russia announced the revival of its Cold War global network of ground-based observatories that monitored all orbiting objects. Russia had deactivated these observatories in the 1990s after the Soviet Union dissolved and formed 14 new nations. Russia has arranged to revive some of the observatories in former parts of the Soviet Union as well as ones it maintained in foreign countries (Bolivia and Mexico). Russia will expand the network with new observatories in eastern Russia. This network tracks more than 5,000 objects, including spacecraft and new satellites.
This observatories decision follows one in mid-2016 when Russia announced it was going to make public its database of known objects in orbit around the earth. This would include all its own satellites as well as non-Russian satellites it had located and was tracking. Russia proposed that other nations who put satellites in orbit do the same and let the UN manage this master database. Russia pointed out that the database it is putting online lists 40 percent more objects than any publicly available American database and that this is largely because Russia has more telescopes and radars watching orbital space plus observers operating from locations all over the largest nation on the planet.
The United States has a classified database of all satellites it knows about, including their status (active, inactive, and when some are about to plunge to earth). The United States did not jump at the opportunity to join this unclassified master database because that would mean revealing satellites that have managed to keep their location secret. The U.S. is more concerned about not letting China know where it's hidden satellites are. Russia is no longer able, because of shortages of cash and tech, to put up as many satellites as it did during the Cold War. The U.S. sees China as the new threat and has already accused China of putting secret anti-satellite devices in orbit. China and Russia are allies and the U.S. does not trust either of them to keep their promises. Russia is pitching this database idea to the UN as a positive step in policing international agreements to not weaponize space. None of the other nations that can put satellites up trust China either but Russia has nothing to lose and much to gain by making an issue of its proposal in the UN. The activity of Kosmos-2519 and its sub satellites over the last year show that Russia is still a contender in the area of killsats (killer satellites) and efforts to control what goes on in orbital space.
Despite the continued secrecy about some satellites, all three nations are more willing to share debris data and warnings. There are a lot of people keeping an eye on this clutter. The U.S. Air Force Space Surveillance Network, which tracks objects 10mm and larger, stopped sharing all of its information in 2004, for national security reasons. That changed when the newly created U.S. Space Force absorbed the Air Force Space Surveillance Network and much else in 2019. The Russian Space Surveillance System is known to use radar to track over 5,000 objects in low orbit. Until recently the Russians have never shared this data completely or regularly. Filling in the gaps are two international organizations, IADC (Inter-Agency Space Debris Coordination Committee) and ISON (International Space Observation Network). IADC is a government operation, whose members include the U.S. NASA and the equivalents in Russia, China, and several other major nations. Like most government organizations, not all data is shared.
ISON is a non-government organization, and they come up with some of the most interesting stuff. ISON comprises 18 scientific institutions, 18 observatories, 25 telescopes, and over a hundred professionals. ISON does not, as far as anyone knows, withhold data because of any national security concerns. ISON work is monitored, and complemented, by the efforts of thousands of amateur astronomers and orbital addicts who connect via the Internet and constantly scour the orbital space for new objects and dangerous movements by existing ones.
ISON has already spotted more than 200 larger (over 10mm) objects that have never been reported by any of the government organizations. The Internet based amateurs are often the first to spot a lot of this new activity, mainly because they have more eyeballs, and, in some cases, impressive optical equipment searching the skies.
When someone spots an object headed for a maneuverable satellite, the owner is alerted and the bird is moved if possible. This has happened several times in the last few years. The number of dangerous objects up there increases 10-20 percent a year. That's even with many of them falling into the atmosphere and burning up each year. Apparently, no one was able to predict the 2009 collision between Cosmos 2251 and the Iridium bird, nor the more recent collision, largely because the high speed of these objects, and slight instability of their orbits can turn an expected near miss into a direct hit.
Now it’s not the accidental encounters you have to worry about but the deliberate ones. While satellite spotters eventually locate and identify anything put up there few objects are observed 24/7. The Russians could simply pick a time when a target satellite was least likely to be observed and send in their maneuverable spy sat to do whatever it needs to do and then change orbit and disappear for a while. Such deliberate encounters are a larger worry than accidental ones. These maneuverable satellites are described as built for repairing or refueling existing satellites. They can also be used to push dead satellites into a lower orbit that will force it into the atmosphere and burn up. These maneuverable satellites can be used to spy on satellites of other nations and make excellent killsats that do their work without causing debris. There is no similar tool for eliminating all those orbital fragments, which are a danger to everyone’s satellites.