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YM COLUMN ARCHIVE

February 18, 2009

Traffic accident at the altitude 800km

At 1:55am on last February 11 (JST), American and Russian satellites collided each other at the altitude 800km over Siberia. The collision seems to have caused several hundreds space debris flied wide apart in space. American satellite was the communication satellite Iridium (500kg) for satellite telephone launched in 1997 while Russian’s was also communication satellite Kosmos 2251 (900kg) launched in 1993. Kosmos 2251 went out of service since three years after the launch. There is no such ruling regulation as “through highway” in space, so both parties are equally to blame.

One of the major accidents in space was that French communication satellite Celine hit large fragments of rocket on the orbit to have instantly broken down in 1997, and minor ones have been frequently happening between satellites and small space debris. However, the collision of this magnitude in space is not within my recollection.

The range of the fragments flied apart in all directions caused by the collision this time is deemed to be over the altitude 400 ~ 3,000km. As the orbital altitude of Japanese Experimental Module Kibo installed on International Space Station (ISS) is 400km, NASA is now under thorough investigation if the damage done to earth observation satellites and ISS.

Incidentally, Iridium Corporation is operating sixty-six “Iridium satellites” to provide global satellite telephone service, and just one loss this time seems not to cause serious damage to the corporation which is, however, to make ready a substitute to replace the lost one.

Among satellites going around the earth, the manned satellites must be carefully attended with caution, particularly when astronauts are engaged in extra vehicle activities. Ground control center is paying special attention to the manned satellites, and when serious dangers are expected from prospective collisions, they temporarily change the orbit to avoid accidents. I heard that space shuttle takes crash avoidance behaviors five or six times in one mission. Traffic control is such a serious matter in space.

And now let me briefly talk about space debris highlighted this time.

Mankind has sent over six thousand satellites to the orbits ever since the then USSR launched the world first satellite Sputnik onto the orbit in 1957. Those satellites, however, do not stay on the same orbits ever after.

The atmosphere surrounding earth is said to range up to 100km normally, but actually it reaches further high, getting thinner in air though. Satellites are moving in thin air all time; therefore, they lose energy little by little because of air resistance to have consequently reduced orbit. When they descend to the level 100 to 150km, they accelerate falling down to the earth due to thick air and most of them burn up in the atmosphere on the way down.

Many of them, however, remain on the orbits even after they are broken down or ran out of battery/fuels for flight control to have become no longer serviceable as satellites. In addition, many parts or fragments of the rockets that carried satellites to space and/or those caused by some other reasons are wandering about on the orbits at high speed.

According to the announcement of Integrated Space Operation Center of U.S. Strategic Command (SATCOM), the number of actually working satellites is eight hundred as of now. The other objects other than the above are garbage, so to speak, and so they are collectively called “space debris”. They are flying at such high speed that even one-centimeter space debris can destroy a satellite; ten centimeters can potentially give serious damage even to ISS, so that SATCOM is constantly on alert by tracking after about thirteen thousand airborne objects all the time.

http://www.technobahn.com/cgi-bin/news/read2?f=200902121034&photo=zoom

According to the observational research so far, the number of the debris exceeding ten centimeters observable from earth is approximately seven thousand; 1 ~ 10 centimeters is about two hundred thousand; if included smaller ones less than 1 millimeters, it counts as many as three million five hundred thousand. Town garbage is surely better collected, but space debris is hard to find its effective way to sweep them all. People concerned about the problem all over the world are keeping their efforts to reduce debris as much as possible including various measures taken at the time of launching.

More or less one hundred satellites are being launched every year; accordingly space debris is rapidly increasing. The accident this time occurred soon after the warning issued by NASA on the increase of potential possibility of collision year by year.

Report from Sydney, Australia: The aging Russian space station “Mir” is maneuvered to be down to the earth next month in the way as if to throw a basketball to the ring, and this time its ring is vast empty ocean between New Zealand and Chili.

In 1972, four mysterious 14kg gas containers made of titanium fell offshore the South Island of New Zealand. Local scientists concluded that these spherical containers inscribed with Cyrillic alphabets were from the spacecraft of the then USSR. It was presumed from its fall timing that the gas vessels probably belonged to the explorer heading for Venus. American specialists were shocked by the advanced technology applied to titanium. It was far superior to the American technology then prevailing. The space law effective then stipulated that the containers had to be returned to USSR who, however, did not acknowledge the objects as of her properties, which gave New Zealand a headache how to cope with the problem. As a result, the containers had to be given back to the farmers living in the farm area where the objects landed because they wanted to have them as heavenly gifts.

In 1978, another major accident took place in Canada where the then USSR’s military satellite “Kosmos 954” loaded with atomic furnace crashed down to have spread radioactive fragments causing contaminations all over.

In 1979, the parts of Skylab fell on the desert region far from outskirts of Perth, Australia. Seventeen-years-old young man by the name of Stan Thornton found the several fragments of Skylab pierced to the roof of his house and jumped onboard the plane bound for San Francisco. Upon arriving in San Francisco he ran into the editorial office of “San Francisco Examiner” and got the reward of ten thousand dollars for presenting the fragments of space station to the publishing company before to anyone else.

Most recently on March 23, 2001, I suppose it is still in everyone’s memory that Russian space station Mir was controlled to guide it down, after having entered the atmosphere, to the empty south Pacific in accordance with the previous plan in spite of all the fuss on earth. I, then controlling the fuss of this country, said at the press conference after the fall of Mir, “I would like to address to the students taking entrance examinations, please forgive the adults who have repeatedly kept saying ‘fall down, fall down’ (pun for failing in exam) by ignoring all of your hard efforts for exams” which was received by big cheers. Now it’s eight years since then.

I welcome your opinions on this column to the following E-mail address.
matogawa@planetary.or.jp

(Translated by The Planetary Society of Japan)