TDRSS info
Jeffrey C. Hunt (jhunt@eagle1.eaglenet.com)
Wed, 21 Feb 1996 07:50:30 -0500 (EST)
The following letter answers some questions I had about the
Tracking & Data Relay Satellite System. Previous information that
I had came from Dave Ransom's STSPLUS satellite tracking software
documentation and from a very informative press-kit released by
NASA last year when they launched TDRS-7. It seems the TDRS
constellation is changing again.
The indented lines are my questions to Steve. Steve works at the
TDRSS White Sands Ground Terminal.
He was kind enough to allow me to past this info on to SeeSat-L but
I have removed his full name and address (my idea-not his).
SAT USSPACECOM ID
TDRS-1 13969
TDRS-3 19548
TDRS-4 19883
TDRS-5 21693
TDRS-6 22314
TDRS-7 23613
Jeff Hunt <jhunt@eagle1.eaglenet.com>
--------------------message---------------------------------------
Greetings, Jeff!
Here's answers to your TDRS questions. I hope they're helpful!
>Thanks for your response. I didn't know more TDRS's were
>planned.
The next generation TDRS are currently called HIJ ... simply the 3
follow-on letters to the 7 birds that have been launched already [TDRS-2
disappeared with Challenger]. Sequential NASA spacecraft names typically
tack on a sequential alphabetic character while they're still on the
ground; after launch, they're supposed to transition to a numerical
sequence. Hence, TDRS-1 is aka TDRS-A, ..., TDRS-7 is TDRS-G. We also get
lazy and refer to them as 'F1', etc ['F' being for 'Flight'], by their
4-digit SIC (Spacecraft Identity Code) [1299 + TDRS-number ... 1300, 1302,
1303, ..., 1306], or by their 7-digit International Vehicle Identity Code
which correlates to the year of launch, the x-th vehicle launched during
that year, and if it was the primary or supplemental payload [for instance:
TDRS-5, Sat-E, F5, 1304, and 9105402 all refer to the same spacecraft
(9105401 was the shuttle that carried TDRS-5 up into orbit, and it was the
54th recorded world-wide launch in 1991).
The first 7 vehicles were built by TRW, but the contract for the newer
birds was won by Hughes -- so their spacecraft will look fairly different
from the first 7, and somewhat similar to other communications satellites
being built by Hughes. I can't remember off the top of my head whether HIJ
will be on a 601 or a 602 bus, or if I've even gotten the bus-number
correct.
>I do know that an alternate communications site is
>being built out there in the SouthWest somewhere, I believe not
>too far from White Sands.
The original site is called 'White Sands Ground Terminal' (WSGT [pronounced
by those-in-the-know as 'whizget']). The newer site is the 'Second TDRSS
Ground Terminal' (STGT [pronounced as 'stee-get']). And, the third site
(gotcha on that one, huh!) is the 'Extended TDRSS Ground Terminal' (ETGT
[pronounced as 'Ee-T-Gee-T']). All 3 sites now comprise the White Sands
Complex (WSC), and we're taking over more and more of the White Sands Test
Facility [the latter is an entirely different NASA organization where they
like to play around with rocket fuel, explosives and the like ... they also
supported the initial DC-X test firings before that vehicle moved over the
hill to the White Sands Missile Range].
The WSC is about 20 miles due east of Las Cruces along Route 70, and 6-10
miles north of the highway ... we're on the west side of the San Andres
mountains [the military Missile Range (whiz-mir) is on the east side], and
strategically situated so that the steerable ground antennae can peek
between some of the mountain saddles. ETGT is a short couple-hundred yards
away from WSGT, but STGT is about 3 miles further north from them both ...
again, mostly placed for an eastward view 'thru' the mountains, I think.
ETGT is a small, crammed building that was tossed on-line to help keep in
touch with all the birds during the STGT and WSGT upgrades. STGT has been
up and running for over a year, now, and is functioning quite well.
Shortly after STGT became operational, WSGT officially shut down operations
in order to be rebuilt. Most of its 1970's era computers have been
removed, and it has been reshaped in STGT's image. WSGT just came back
on-line on January 5 and is undergoing testing ... it should be officially
functioning by mid-year -- if not quite a bit sooner. Word has it we're
VERY far ahead of schedule on its upgrade, and making good brownie points
with NASA for actively saving big bucks.
The official gossip was that WSC was situated out here since it has one of
the smaller amounts of rainfall on record in the continental U.S.of A.
However, based on my 3-4 years of living and working here, them rockets and
things that NASA has launched have poked too many holes in the atmosphere,
or something. Not only does it rain (and snow) quite a bit out here -- but
it does it significantly more up at work than it does down here in the
valley (about 1000 feet in elevation difference). Personally, I'm amazed.
>1. TDRS 1 has been drifting East for some time. Has its
>communications life ended? The last I heard it was supporting
>limited communcations in the Antarctic.
TDRS-1 will (finally) stop drifting in the 49-degrees West longitude
region, and is currently being planned for supporting ELVs (expendable
launch vehicles). It also has taken over (again) as TDRS-Spare ... ooops,
another definition to expound upon. Up to now, 3 of the TDRS have always
carried an '-East', '-West' or '-Spare' designation ... F5 = TDRS-West, F4
= TDRS-East; F7 was TDRS-Spare until a week or so ago.
F-1's communications life has definitely NOT ended, but it is also the
oldest and most fragile of the 6 birds [it suffered some severe physical
problems after deployment from the shuttle when the first IUS (Inertial
Upper Stage) malfunctioned]. It also has the least amount of fuel and the
greatest orbital inclination, and we're nurse-maiding it along as much as
possible.
Not only did F-1 support Antartica testing, but it also filled in the ZOE
for the first time (Zone of Exclusion ... the area over near India that
cannot be seen by either TDRS-East or TDRS-West). The ZOE is now covered
by TDRS-3.
By the way ... WHERE do you people out in the real world get any
information on TDRS? [I'm referring to your statement 'The last I heard',
above.] I wouldn't mind having a better grasp of following what the public
thinks is going on.
>2. TDRS 3 I understand has been supporting the Compton
>satellite. Does it still support the STS mission in any limited
>manner. The positions of TDRS 4 and 5 leaves a communications
>gap for LEO sats between East Africa and China.
Filling in the ZOE is an on-going process; GRO has gotten the most benefit,
but we just recently did a Hubble test, also -- and the Shuttle has taken
advantage of the ZOE closure a lot! I'm too close to the situation to know
anymore what NASA's current goal is, but I believe that closing of the ZOE
will be VERY desirable once the Space Station support begins. [Just
because I work out here doesn't mean that they tell me very much ... I was
serious about wanting to know how you know things!]
>3. I realize your site at White Sands is in view of all TDRS's
>except TDRS 3. Am I wrong or correct in understanding that
>originally three TDRS's would be equally spaced around the globe?
Unfortunately, you're wrong ... probably mislead (like I was) by gleams of
Arthur C. Clark concepts. The original philosophy was for primary
TDRS-East and -West vehicles, with the ZOE as an acceptable loss of
coverage (TDRS-Spare would sit between the 2 and be available for hot
backup). After all, up until TDRSS, ground stations were literally
scattered about the globe ... if I remember right, the ground stations
offered 10-15 minutes or so coverage of a 90+ minute orbit. TDRS would be
able to cover up to 90-95% of the same orbit, while presumably saving more
big $$ by being able to shut down all those scattered sites and consolidate
out here in the (sometimes) sunny southwest.
The next philosophical iteration focused on handling more than 3 vehicles,
so co-locating 2 birds at each -East, -West and -Spare region was the
official goal. [Note that all 3 of these locations are directly viewable
from White Sands; the ZOE is not, and that was deemed a security risk not
worthy of the price.] Currently, TDRS-4 and -6 are co-located in the east
[and -6 will probably carry the official -East designation in the very near
future]; TDRS-7 will shortly be moved westward to live close to TDRS-5.
Much thought is still going into what-to-do with the ZOE closure, but
TDRS-3 will surely remain there for quite a while. Just wait and see how
much activity increases once Space Station work begins, though!
This was fun ... I hope the answers are useful, and don't digress too much
and/or over-burden you with details. If you have anything else to ask --
fire away!
I think I'll copy this to the astro list, too, in case it's of interest to
others! [See what happens when you make me think about work!]
Steve