In the TBUS bulletin Part IV, all information
necessary to calculate a satellite’s orbit and variations
in the orbit is provided. This information includes an
epoch orbit number, two forms of an epoch date,
position and velocity coordinates, the nodal period,
and anomaly values used to determine the change in
position of the satellite over any period of time.
SAT MOD Ephemeris Updates
Like the TESS, the SAT MOD may update
ephemeris information by reading a TBUS message
file. If the appropriate TBUS bulletin is not available
directly from a disk file, the system may be updated
with manual entries by using information in the TBUS
bulletins. Only certain elements from each TBUS
bulletin are required for each satellite in the SAT
MOD. The resulting ephemeris files need only be
updated every 2 weeks.
Instructions for imputing
TBUS bulletin data is contained in the IMOSS user’s
guide.
TESS Ephemeris Updates
TESS allows satellite ephemeris data files to be
updated manually by entering selected data via the
keyboard. TESS, interfaced with a communications
system, may be directed to read a saved TBUS message
file to automatically update ephemeris information.
TESS may only use each particular TBUS bulletin
during a 7-day valid period following the prediction
date; in this case January 05 to January 12. Since
predict bulletins are sent out daily, TESS may store
more than one file of ephemeris information for each
satellite, and prediction periods may overlap.
AN/SMQ-11 Ephemeris Updates
The AN/SMQ-11 does not have the capability to
interpret imported TBUS messages to update its
ephemeris files. Various parameters from the TBUS
bulletin Part IV may be manually entered. The SMQ-
11 requires the epoch calendar date-time-group be
entered vice the epoch decimal date-time-group.
NASA TWO-LINE DATA
Another predict message is the NASA Two-Line
Orbital Elements (TLE) bulletin. This bulletin
contains orbital information very similar to Part IV of
the TBUS bulletin. The message is divided into 16
elements and can be input into the SAT MOD and
AN/SMQ-11 in lieu of TBUS data. Keep in mind that
while similarly named elements appear in both the
NASA Two-Line and TBUS bulletins, the values are
NOT interchangeable between systems to compute
satellite tracks. Table 1-4 is an example of a NASA
Two-line bulletin and table 1-5 is a description of the
information.
NAVSPASURCEN ORBITAL DATA
The Naval Space Surveillance Center
(NAVSPASURCEN) in Dahlgren, Virginia, tracks all
U.S. and foreign-operated satellites and space debris.
Navy and Marine Corps satellite-receiver system users
may request message support for satellite tracking
information. The AN/SMQ-11 contains software
designed to use and interpet separate messages of data
known as Satellite Equator Crossings. TESS uses a
product known as C-Element Orbital Data to calculate
orbits for the AN/SMQ-11.
A Satellite Equator Crossings message contains
information similar to TBUS Part I. The AN/SMQ-11
needs to be updated frequently (about every 2 days) by
using the information from this product. The message
contains information on all U.S. and foreign-operated
environmental satellites. Table 1-6 contains a portion
of a Satellite Equator Crossings message with
explanations of the elements required to update the
AN/SMQ-11. The underlined elements are required
input.
C-Element orbital data also contains information
similar to Part IV of the TBUS bulletin. See table 1-7
for an example of a typical message containing C-
element orbital data and table 1-8 for an explanation of
the data. In the C-element orbital data message, each
line of data is repeated three times. This is done so that
Table 1-4.—Sample NASA Two-line bulletin
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