Atlas Centaur Rockets
Jason Hatton (jason.hatton@etss.u-strasbg.fr)
Sat, 04 Apr 1998 13:46:37 +0000
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Dear All,
There have been a number of recent posts to SeeSat about observations
of flashing Centaur rockets, so I decided to do some research &
determine how many of these are potentially observable. I've observed
several of these recently & they are IMHO some of the easiest objects to
observe in high eccentricity orbits.
Atlas Centaurs are relatively large upper stage rockets, most of which
are initially in geostationary type transfer orbits (ie. an apogee of
36000km & a perigee of a few hundred km). What is of interest to visual
satellite observers is that many flash & so can easily observed at
ranges of 10,000km or more in binoculars or small telescopes often
flashing at mag +6 or brighter. For people lucky enough to see these
objects at perigee (100 - 600km) they can be very bright indeed (mag
+1). The Atlas Centaur & Atlas-I Centaurs are cylindrical 10m x 3m
rockets with a bare metal surface, whilst Atlas-II Centaurs are 15m x 3m
& covered with an orange foam. If this is anything like the material
covering Shuttle external tanks it may darken with exposure to sunlight
& so could alter the flash pattern of the rocket. Centaurs have also
been launched on by Titan rockets, those on Titan-IIIE rockets are
fairly similar to Atlas Centaurs, whilst those launched on Titan-IV's
have a larger (5m) diameter.
I used the Atlas Centaur launch record, Jonathan's space report,
alldat.tle & the PPAS flash measurement database to draw up a list of
potentially observable Atlas Centaurs (no time yet to do the same thing
for Titan-Centaurs). This list is given below. There are several things
of interest;
(i) Most of the Atlas Centaurs which have been observed flash
(ii) Most pre 1978 launched Centaurs are in stable GTO orbits
(600x36000km)
(iii) Most of the recently launched Centaurs have been put into transfer
orbits which decay rapidly (ie. perigee's of 100-200km) despite very
high apogee's (some up to 80,000km)
(iv) There are several Centaurs in LEO. Starting later this year some
Atlas Centaur launches will be made in to Polar LEO from Vandenberg, so
we may well be treated some nice easily observable flashing satellites!
There are elements for 57 Atlas Centaurs (& several Titan Centaurs) in
alldat.tle, obtained from Mike McKant's web site. Several of these are
likely to decay in the next couple of years & two (Goes 10r & DBS 2r)
are predicted to decay this month. If your planning on observe these &
other Centaurs with low perigee's it's probably a good idea to get fresh
elements, since the orbital period can decrease quite rapidly.
I hope this is of interest / use for observing
Best wishes & clear skies,
Jason
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Potentially observable Atlas Centaur Rockets (3-Apr-98)
Table best viewed with "word wrap" turned off.
(a) Atlas Centaurs
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Norad Common Flash Year 2yr
ID Intl. Desn. Name (r) incl. period Period Meas. Decay? Notes
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694 1963-47A Atlas Centaur 2 30.4 104 42.6 1997 N
698 1963-47D AC-2 deb 29.9 106 0.5 1997 N Deb
700 1963-47F AC-2 deb 30.5 108 67 1995 N Deb
701 1963-47G AC-2 deb 30.0 105 1.88 1995 N Deb
739 1963-47H AC-2 deb No obs. N Deb
3598 1968-110B OAO-A2r 30.5 99.5 5 1993 N
4069 1969-69B ATS-5r 17.2 703 8.77 1997 N
4882 1971-06B Intelsat-4-2r 28.2 650 5.6 1997 N
6779 1967-001X* Intelsat-4-3r 28 650 9 1997 N
5816 1972-03B Intelsat-4-4r 28 650 1.5 1994 N
6058 1972-41B Intelsat 4-5r 27.5 650 25.4 1997 N
6155 1972-65B OAO-3(C)r 35 98.6 S 1993 N
6797 1973-58B Intelsat-4-7r 28 650 3.19 1998 N
7545 1974-93B Intelsat-4-8r 26 650 ? 1994 N
7902 1975-42B Intelsat-4-1r 26 650 lp 1982 N
8331 1975-91B Intelsat4A-1r 21.6 651 7.3 1983 N
8621 1976-10B Intelsat4A-2r 21.8 650 lp 1983 N
8840 1976-42B Comstar-1 (1A)r 21.2 650 4.7 1997 N
9329 1976-73B Comstar-2 (1B)r 21.3 650 19.75 1991 N
10025 1977-41B Intelsat4A-4r 21.3 650 4.56 1983 N
10722 1978-02B Intelsat4A-3r 21.5 650 lp 1991 N
12908 1978-16C FLTSATCOM F1Deb 26.4 170 18.5 1996 ? Deb
10779 1978-35B Intelsat4A-6r 21.8 650 ? N
10976 1978-68B Comstar-3 (1C)r 21.4 650 N
12069 1980-87B FLTSATCOM F4r 26.1 162 7.37 1996 ?
12445 1980-98B Intelsat-5-2r 23.7 225 12.62 1998 ?
12363 1981-18B Comstar-4 (1D)r 20.7 650 2.99 1997 N
12497 1981-50B Intelsat-5-1r 23.6 210 4.96 1996 ?
13007 1981-119B Intelsat-5-3r 23.6 210 6.02 1997 ?
15631 1985-25B Intelsat5A-10r Decayed?
15874 1985-55B Intelsat5A-11r 23 530 17.82 1997 ?
16102 1985-87B Intelsat5A-12r 23 465.6 3.89 1996 ?
(b) Atlas I
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Norad Common Flash Year 2yr
ID Intl. Desn. Name (r) incl. period Period Meas. Decay? Notes
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20713 1990-65B CRRESr 17 575 No obs ?
21907 1992-13B Galaxy 5r 19.7 640 No obs N
22564 1993-015B UHF-F1r 27.2 137.3 2/2000
22788 1993-56B UHF-F2r 6.83 1997 Decayed?
23133 1994-35B UHF-F3r 26.9 250 34.2 1996 ?
23858 1996-27B SAXr 4 94.9 No obs 5/2000
24787 1997-19B GEOS-K(10)r 27.4 417 No obs 4/1998
(c) Atlas II
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Norad Common Flash Year 2yr
ID Intl. Desn. Name (r) incl. period Period Meas. Decay? Notes
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21804 1991-83B Eutelsat-II-F3r 17.5 753 No obs N (a)
21874 1992-06B DSCS-III-B01r No obs Decayed?
21990 1992-32B Intelsat-K r 26.3 434 No obs ?
22010 1992-37B DSCS-III-B10 r No obs Decayed?
22928 1993-77B Telstar-401r 23.6 335 No obs 2/2000
23193 1994-047B Direct TV D2 r 26 109 6.6 1998 4/1998
23414 1994-79B Orion Atlan.F1r 30.6 2880 No obs N
23468 1995-03B EHF-F4r 26.8 470.3 150 1995 ?
23529 1995-13B Intelsat 705r 26.7 274.1 No obs 10/2000
23554 1995-19B AMSC-1 r 26.1 510 No obs ?
23590 1995-27B EHF-F5 r 26.9 450 25.4 No obs ?
23629 1995-38B DSCS-III-B5 r No obs Decayed?
23658 1995-43B JCSAT3r 22.8 1640 No obs ? (b)
23697 1995-57B EHF-F6r 26.7 470 6 1995 ?
23742 1995-69B Galaxy 3R r 26.7 470 No obs ?
23780 1996-06B Palapa C1 r 21.7 1916 No obs ? (b)
23840 1996-20B Inmarsat-3-F1 r 21.5 640 No obs N
23968 1996-42B UHF-F/O-F7 r 26.9 471 No obs ?
24316 1996-54B GE-1 r No obs Decayed?
24666 1996-67B Hot Bird 2 r No obs Decayed?
24675 1996-70B Inmarsat-3-F3 r 22.2 650 No obs N
24773 1997-07B JCSAT-4r No obs Decayed?
24881 1997-36B Superbird C r 25.6 1664 No obs ? (b)
24937 1997-50B GE-3 r 18.7 790 No obs N
25005 1997-59B Echostar-F3 r 25.9 101 No obs ? (c)
25020 1997-65B IABS/DSC-III r 26.1 550 No obs 7/1999
25087 1997-78B Galaxy 8i r 26.1 811 No obs 11/2000
? 1998-05B "Capricorn" r Classified elements** No obs ?
Key:
incl. = orbital inclination
Period = orbital period
Flash period = measured flash period in seconds from PPAS database
lp = long period
Year Meas. = year of most recent flash period measurement,
No obs. = no observations reported
2yr decay = SATEVO predicted date of decay in next two years
N = decay unlikely in near future
? = perigee less than 400km, so decay possible in next few years
Decayed? = no elements in alldat.tle, so probably decayed in last 9 months
Notes:
(a) = listed as "Ariane rocket"
(b) = old elements, possibly decayed or "lost"
(c) = probably decayed in last 2-3 weeks
Deb = Debris or fragment
* Origonal Intl. Desn. = 1971-116B
** The "Capricorn" rocket is in an approx. 45 deg incl. high eccentricity orbit.
What a shame that the elements are classified!
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