Card 6t - ORBDEF3 Solar and Orbit Parameters

This optional card defines the solar and orbit parameters for a spacecraft.

Parameter Value Description
ORBDEF3 ORBDEF3 or 43 mnemonic or 43
ID integer ID number
SOLFLUX real Solar flux value
integer Solar flux table number for SOLOPT=TABLE
SOLOPT SUNDECL SV1 is sun's declination angle in degrees
MEQUI Planet is Earth, time is March equinox
JSOL Planet is Earth, time is June solstice
SEQUI Planet is Earth, time is September equinox
DSOL Planet is Earth, time is December solstice
SUNRA Planet is Earth, SV1 is sun right ascension angle in degrees
DAY Planet is Earth, SV1 is day number for Earth for year (year=1999)
GMT Planet is Earth, SV1 is day value
TABLE SOLFLUX is a solar flux table number
SV1 integer Day number for SOLOPT=DAY or SOLOPT=GMT
real Angle in degrees for SOLOPT=SUNDECL, SOLOPT=SUNRA
0 For all other SOLOPT options
SV2 integer Month for GMT option
SV3 integer Year for GMT option
SV4 integer Hour for GMT option
SV5 integer Minutes for GMT option
SV6 integer Seconds for GMT option

SOLFLUX

SOLFLUX is the incident solar flux value of the planet, or table number of the time-dependent solar flux value defined in Card 9 TABTYPE.

If a table is defined, the dependent parameter on the TABTYPE Card must be QNODE, and the independent parameter must be TIME.

SOLOPT

SOLOPT is the flag for defining the sun’s angular position with respect to the planet.

For planets other than Earth, SOLOPT = SUNDECL must be used, and it is also necessary to define the sun right ascension angle on ORBDEF5 Cards.

SV1

This field specifies the:

  • Day number if SOLOPT = GMT (Greenwich Mean Time) or SOLOPT = DAY.
  • Sun declination angle value in degrees for SOLOPT = SUNDECL. This is the angle in degrees between the sun vector, which points towards the sun, and the equatorial plane. It is > 0 in the Northern and < 0 in the Southern hemispheres. For Earth, the sun’s declination angle is between ± 23.44 degrees. Refer to the diagram in Card 6l - Additional Orbital Parameters ORBADD Card – Optional.
  • Sun's right ascension angle in degrees for SOLOPT = SUNRA. The sun right ascension angle is the angle measured eastward from the vernal equinox axis in the Earth's equatorial plane to the projection of the sun vector onto the equatorial plane. The vernal equinox is the time when the apparent position of the sun crosses the equator moving from south to north. The vernal equinox axis is a line from the Earth's center to the point where the sun crosses the equator moving from south to north.

SV1 must be 0 for all other options.

SV2

SV2 is month if SOLOPT = GMT, otherwise it must be 0.

SV3

SV3 is year if SOLOPT = GMT, otherwise it must be 0.

SV4

SV4 is hour if SOLOPT = GMT, otherwise it must be 0.

SV5

SV5 is minutes if SOLOPT = GMT, otherwise it must be 0.

SV6

SV6 is seconds if SOLOPT = GMT, otherwise it must be 0.

Notes

All fields are required on all the Cards, except for the FRONTGRP and REVGRP on ORBDEF1, which may be blank. If the value in a field is to be ignored, specify 0.

A simpler alternate method is available in Cards 6k and 6l.

It is helpful to reference the diagram in Card 6l - Additional Orbital Parameters ORBADD when perusing these cards.

ID is the orbit and attitude modeling request number. ID is an integer value common to all associated ORBDEF Cards.