greenwichsrt

Greenwich mean and apparent sidereal times

Syntax

[thGMST,thGAST] = greenwichSRT(utcJD)

[thGMST,thGAST] = greenwichSRT(utcJD,dUT1,dAT)

Description

[thGMST,thGAST] = greenwichSRT(utcJD) calculates Greenwich mean and apparent sidereal times at a specific Universal Coordinated Time (UTC). Mean sidereal time accounts only for secular motion (precession). Apparent sidereal time includes secular and periodic contributions.

[thGMST,thGAST] = greenwichSRT(utcJD,dUT1,dAT)calculates Greenwich mean and apparent sidereal times at a higher precision using Earth orientation parameters.

Examples

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Calculate Greenwich Sidereal Times

Calculate Greenwich sidereal times at 12:00 on January 4, 2019.

jd = juliandate([2019 1 4 12 0 0]);
[thGMST, thGAST] = greenwichSRT(jd)

thGMST =
  283.8103

thGAST =
  283.8065

Input Arguments

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`utcJD` — UTC as Julian date
scalar

Universal Coordinated Time (UTC) as a Julian date, specified as a scalar.

Tip

To calculate the Julian date for a particular date, use the juliandate function.

Data Types: double

`dUT1` — Difference between CUT and UT1
`0` (default) | scalar

Difference between the Coordinated Universal Time (UTC) and Universal Time (UT1), specified as a scalar, in seconds.

`dAT` — Difference between TAI and UTC
`0` (default) | scalar

Difference between International Atomic Time (TAI) and Coordinated Universal Time (UTC), specified as a scalar, in seconds.

Output Arguments

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`thGMST` — Greenwich mean sidereal time
scalar

Greenwich mean sidereal time, specified as a scalar, in seconds.

`thGAST` — Greenwich apparent sidereal time
scalar

Greenwich apparent sidereal time, specified as a scalar, in seconds.

Limitations

The greenwichsrt function is available only by installing the Aerospace Blockset™ CubeSat Simulation Library from the Add-On Explorer.
This function requires the Mapping Toolbox™ license.