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This looks like this answer because that's where I found this.

Celestrak offers a copy of a Satcat from which a tabulation of space objects can be gleaned:

The legacy text format (uses column numbers instead of the new CSV format) is as follows:

001-011  International Designator
    Launch Year (001-004)
    Launch of the Year (006-008)
    Piece of the Launch (009-011)

So for each year we should be able to count the number of unique "Launch of the year" values exist, and compare it to the highest value to see if they agree.

They do except in 1971 and 2014 where there's a difference of one more launch of the year than the highest launch number. This happened because someone inserted a value of 000 for launch of the year:

1971-000E    05310   D US UNKNOWN 1 DEB          US     1971-01-01  AFETR  1990-09-26   1436.7    1.2   35795   35763     N/A
2014-000A    40328     UNKNOWN LDS DEB           CIS    2014-01-01  PLMSC                710.6   70.5   32069    7930    0.0030

Question: Out of 47,108 lines in the Satcat I downloaded today, why are there exactly two lines with launch of the year of 000? Today there are 98 lines that contain 'UNKNOWN' and 96 lines that contain both 'UNKNOWN' and 'DEB', so that can't be it by itself.

Here's a plot of the data, and the raw numbers below. Please note that it is not accurate for this year 2020 because the year isn't over yet.

launches per year

inelegant script for sorting and plotting https://pastebin.com/GykNkE5Q

tabulated results (year 2020 is incomplete!)

1957 2 2 True
1958 8 8 True
1959 14 14 True
1960 19 19 True
1961 35 35 True
1962 72 72 True
1963 55 55 True
1964 87 87 True
1965 112 112 True
1966 118 118 True
1967 127 127 True
1968 119 119 True
1969 110 110 True
1970 114 114 True
1971 121 120 False
1972 106 106 True
1973 109 109 True
1974 106 106 True
1975 125 125 True
1976 128 128 True
1977 124 124 True
1978 124 124 True
1979 106 106 True
1980 105 105 True
1981 123 123 True
1982 121 121 True
1983 127 127 True
1984 129 129 True
1985 121 121 True
1986 103 103 True
1987 110 110 True
1988 116 116 True
1989 101 101 True
1990 116 116 True
1991 88 88 True
1992 95 95 True
1993 79 79 True
1994 89 89 True
1995 74 74 True
1996 73 73 True
1997 86 86 True
1998 77 77 True
1999 73 73 True
2000 82 82 True
2001 58 58 True
2002 62 62 True
2003 61 61 True
2004 53 53 True
2005 52 52 True
2006 63 63 True
2007 65 65 True
2008 67 67 True
2009 75 75 True
2010 70 70 True
2011 80 80 True
2012 75 75 True
2013 78 78 True
2014 91 90 False
2015 83 83 True
2016 83 83 True
2017 86 86 True
2018 112 112 True
2019 97 97 True
2020 87 87 True
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There is no reason there are exactly two, there happen to be two currently.

As a special case, launch number 000 of the year is used for cataloged objects whose parent launch is unknown. This special case has been used very rarely and most of the relevant cases have since been identified with known launches and given revised designations. I [list] all such cases here.

S02428 1966-000A 1965-058D
S02429 1966-000B 1963-014DG
S02430 1966-000C 1963-014DH
S02431 1966-000D 1963-014AC
S04924 1971-000A 1962 B LAM 2 (1962-059B)
S04925 1971-000B 1964-086B
S04926 1971-000C 1964-086C
S05309 1971-000D 1965-108H
S05310 1971-000E maybe should be 1971-039D?
S40328 2014-000A unknown Oko debris

source

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