Keywords: meteor shower, space debris, space safety
Maybe you have seen spacecrafts being hit and destroyed by space debris, causing disasters in sci-fi movies. For example, in the Russian movie Attraction, an alien’s spaceship was damaged by a meteor shower and was then shot down by Russian Air Force as NATO spy spacecraft, causing it to crash into several buildings in Moscow, killing hundreds of people. Another instance would be the UK film Gravity in which a NASA spaceship's connection with Mission Control was lost after space debris destroyed many communication satellites.
Source: NASA Orbital Debris Program Office, photo gallery
These sci-fi plots do not come from nowhere. In reality, meteoroids and space debris do pose a threat to astronauts and spacecrafts. In recent years, events such as collisions and military testings dramatically increased the number of space debris, posting even greater threats to artificial satellites and all sorts of space objects in Earth orbit.
According to ESA's Space Debris Office, the number of debris objects estimated by statistical models to be in orbit are (information correct as of Jan 2019):
34, 000 objects >10 cm
900, 000 objects from 1 cm to 10 cm
128 million objects from 1 mm to 1 cm
These huge, intimidating numbers probably make the so-called “Kessler syndrome” not so ridiculous as it may seem. This theory proposed by NASA scientist Donald J. Kessler in 1978 states that if the density of objects in low Earth orbit (LEO) is high enough, collisions between objects could cause a cascade where each collision generates space debris that increases the likelihood of further collisions. This kind of domino effect and positive feedback could potentially render space activities and the use of satellites in specific orbital ranges impractical for many generations.
However, though space agencies have been attempting to mitigate this potentially hazardous situation, their endeavours remain somewhat limited due to political, legal, economic and cultural reasons. Not to mention the fact that many invented methods for removal of space debris are only in theory, "Companies Have Technologies, but Not Business Plans, for Orbital Debris Cleanup" as there is not much commercial incentive.
Here is when what we dread—spacecrafts being hit—really happens. Olympus-1, a former communications satellite built for ESA in the 1980s had been the largest civilian telecommunications satellite ever built at the time of its launch and was sometimes referred to as “LargeSat”. On 11/12 August 1993, the satellite lost earth pointing attitude and began spinning, which was later followed by the loss of an on-board gyro. This malfunction was because the satellite was hit and damaged by a small piece of the comet 109P/Swift-Tuttle during the peak of the Perseid meteor shower. Subsequent recovery actions consumed too much fuel and could not manage to re-establish service. As a result, it had been decided that the Olympus mission should be terminated and the satellite disposed to GEO disposal orbit.
This month, while the Northolt Branch Observatories in London, UK was doing measurements to the comet C/2018 Y1 (Iwamoto), Olympus-1 accidentally crossed the camera’s field of view.
"We find a rotation period of 68.4 ± 0.8 seconds for OLYMPUS-1, and a very large lightcurve amplitude (>3 mag), probably due to reflection off the satellite's large solar arrays", says Northolt Branch Observatories on Facebook.
The camera that Northolt Branch Observatories used in obtaining the measurements was QHY42, a scientific CMOS camera designed and produced by QHYCCD.
QHY42 uses the Gsense400 Scientific CMOS sensor with extraordinary 95% peak QE, 79% UV QE and very good NIR response, plus 22.5mm x 22.5mm sensor size, 11um pixel size and 89ke- full well capacity. Readout noise being as low as 1.7e- together with high QE make it possible to achieve high SNR even when imaging dim objects—only 5 photons produce a SNR>3. In addition, QHYCCD has adopted advanced technology to reduce amplifier glow and the absence of microlens on each pixel avoids the influence on photometry.
These exceptional features make the camera ideal for astronomical and other scientific research.
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