Description of the orbital data files


Two types of the orbital data are presented:
  • the orbital data used for the flight operation monthly (m) long-term planning,
  • the after-flight (a) orbital data, used during data treatment and archiving.

The orbital calculations are based on the initial orbital data determined by KIAM RAN using the orbital radio measurements treatment.The determined initial orbital data are presented as a state vector (satellite position and velocity) in the J2000 reference.

The satellite position in the various coordinate systems and different parameters along the orbit as a function of time are shown. The orbital information for each month is presented in the separate directory.
The calculations for the "m" stage of some month "yymm" are available one or two month before this month.
Later this data are added or replaced by aposteriory orbital calculation.


Introduction

There is a significant difference between satellite motion prediction during flight operation and aposteriory satellite motion calculation.

The orbit disturbance by the attitude control do not permit to use determined initial orbital data (orbital parameters) for long term prediction of the satellite motion.

In fact each set of the orbital parameter corresponding to the epoch T(i) is valid on the time interval, which is covered by measurements, used for this determination. As a rule this time interval is located in the left side of the T(i) and covers the time interval T(i-1) - T(i). The satellite position with preciseness 50-km can be calculated in this time interval. Out of the mentioned time interval the errors grows many times.

The orbital calculation for the long term operations monthly (m) planning is based on the satellite motion prediction for two or more month ahead. The extrapolation approach to the satellite motion calculation is used in this case.

During aposteriory (a) calculation the interpolation approach is used. For the time interval between two orbit's determinations connected with time T(i-1) and T(i) the satellite motion is calculated by using "back" integration from T(i) to T(i-1).

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Directories structure

On the STDA server the orbital information for each month is located in the separate directory, which name consists from the year (YYYY) and month (MM) numbers.

The Parent Directory of the Tail Probe orbital data is http://www.iki.rssi.ru/da/interball/tail/orbit/
The Parent Directory of the Auroral Probe orbital data is http://www.iki.rssi.ru/da/interball/auroral/orbit/

For example, the 199808 directory contains the orbital information for August 1998. Each directory includes a set of files, which name and extension indicates its contains and destination.

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The file names' construction

The name of each file consists from the following components:

components

possible values

Comments

stage name

m

corresponds to orbit predictions for one or more month ahead
during flight operations

a

corresponds to the aposteriory orbit calculations
during scientific data treatment and archiving

satellite name

a

INTERBALL Auroral Probe

t

INTERBALL Tail Probe

year and month

YYMM

two last figures of the year number & month number

decade's number
in frame of
the month

d1, d2, or d3

this option is used only for the files with extension '.geo'

For example, the files mt9808.??? contain Tail Probe orbit prediction used during flight operations planning for August 1998.
The files at9808.??? contain the results of the aposteriory Tail Probe orbital calculations for August 1998.
The file at9808d1.geo contain the results of the aposteriory Tail Probe calculations for the first decade (1-10) of August 1998 (with couple of day's extension).

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Flight stage. The orbital data predicted for the flight operations monthly (m) planning

In the mostly of files corresponding to the 'm' stage the orbital information is shown as a function of the Moscow time (MT=UT+3h). In some of them the Universal time is used. See below the file's extension list and the reference to its descriptions.

#

extension

The file contains and reference to its description

function of the time:
UT or Moscow time
(MT=UT+3h)

step

1.

.ind

The initial orbital data, used during orbit calculation

UT

not determined

2.

.nod

The ascending nodes on the Earth's equatorial plane cross-section

UT

draconian period

3.

.se

The satellite positions in the SE & GSM coordinate systems

UT

1 h

4.

.reg

The predicted simulative regions in the satellite positions

MT

1 h

5.

.bgr

The simulative regions' borders cross-section

MT

not determined

6.

.vis

Radio visibility of the satellite for the several groundbased station

MT

1 h

7.

.brv

The visibility zones for the several groundbased station

MT

not determined

8.

.new

The predicted angular positions of the Earth and Moon in the satellite centered solar-ecliptic coordinate system

MT

1 h

9.

.geo

Magnetic mapping footprints coordinates

MT

1 h

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The aposteriory (a) stage. The orbital calculations for scientific data treatment and archiving

Almost in all files corresponding to the 'a' stage the orbital information is shown as a function of the UT. Accept the file with extension '.bgr', where the Moscow time (MT=UT+3h) is used.

See below the file's extension list and its descriptions.

#

extension

The file contains and reference to its description

function of the time:
UT or Moscow time
(MT=UT+3h)

step

1.

.ind

The initial orbital data, used during orbit calculation

UT

not determined

2.

.nod

The ascending nodes on the Earth's equatorial plane cross-sections

UT

draconian period

2.

.se

The satellite positions in the SE & GSM coordinate systems

UT

20 min

3.

.gsm

The satellite positions in the SE, GSM & SM coordinate systems

UT

20 min

4.

.geo

Magnetic mapping footprints coordinates

UT

10 min

5.

.bgr

The simulative regions borders cross-section

MT

not determined

6.

.elm

The osculating elements (as a state vector in the GEI J2000 coordinate system)

UT

not determined

7.

.str

The osculating elements file structure

UT

1 day

8.

.ymd

The time interval covered by the osculating elements

UT

-

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Back to the Space Research Institute (IKI) Satellite Situation Center (SSC)


Dr. Victoria Prokhorenko
Last modified 8 December 1999