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XMM Flight Dynamics
ESOC/FCSD/OAD

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XMM-SOC-ICD-0019-OAD Issue 1.1 September 15, 1998 i XSCS Orbit ICD

XMM
Interface Control Document XSCS Orbit Access Software
XMM Doc. Ref:

XMM-SOC-ICD-0019-OAD

OAD Doc. Ref: OAD-XMM-IA-ICD-ORB-SOC

Issue 1.1 September 15, 1998

Signature Custodian: Agreed: ....................................... ....................................... ....................................... ....................................... Released: .......................................

Date ................... ................... ................... ................... ................... S Pallaschke R E MÝnch N Peccia D Heger H Nye TOS-GFM TOS-GF TOS-GCM TOS-MOX TOS-MOX


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XSCS Orbit ICD - Distribution List

Distribution List
DESIGNATION D/TOS-GF D/TOS-GFO R. MÝnch F. Dreger G. Gienger P. Mahr R. Mugellesi J. Dow S. Pallaschke M. Rosengren A. SchÝtz A. McDonald F. Delhaise S. Kasten H. MÝller P. Gladney C. Greco N. Peccia M. Merri E. Perdrix H. Nye D. Heger P. Maldari M. Schmidt J. Wardill
23

NAME
1

2

3

4

5

D/TOS-GFM

6

7

8

D/TOS-GFS Logica EDS

9

10

11

12

13

Terma D/TOS-GCM

14

15

16

17

18

D/TOS-MOX D/TOS-MOI Serco Total:

19

20

21

22

23


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XSCS Orbit ICD - Document Status Sheet

Document Status Sheet
1. DOCUMENT TITLE:

Interface Control Document - XSCS Orbit Access Software
XMM-SOC-ICD-0019-OAD/OAD-XMM-IA-ICD-ORBSOC 6. REASON FOR CHANGE Initial draft of document. Updated according remarks from J. Dow and S. Pallaschke Updated to include reference to new AMS keywords ICD

2. DOCUMENT REFERENCE NUMBER: 3. ISSUE Draft Issue Issue 4.REVISION 1.0 1.0 1.1 5. DATE 1996/11 1997/10 1998/09


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XSCS Orbit ICD - Document Change Records

Document Change Records
Document Change Records
DCR NO DATE ORIGINATOR 1. DOCUMENT TITLE: 0 September 15, 1998 S. Pallaschke

Interface Control Document - XSCS Orbit Access Software
XMM-SOC-ICD-0019-OAD/ OAD-XMM-IA-ICD-ORB-SOC Issue 1.1

2. DOCUMENT REFERENCE NUMBER: 3. DOCUMENT ISSUE/REVISION NUMBER: 4. PAGE page ix page 7 page 11, 14, 15 5. PARAGRAPH

6. REASON FOR CHANGE Added new ICD to list of reference documents Added reference to new ICD Corrected error codes


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Documentation Tree
RC IA SDD SAD OPF MOD FDR Requirements Compilation Implementation Analysis Software Description Document System Assurance Document Organisation and Planning File Mission Operations Document Flight Dynamics Report


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Table of Contents
Distribution List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii Document Status Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii Document Change Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Documentation Tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .v Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii 1 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Orbit Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1 2.2 3 XMM Orbit Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Orbit Determination Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Overview of Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 3.2 3.3 List of tracking data input files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 List of interface files internal to Flight Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 List of output files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

4

Summary of XSCS interfaces and procedure for delivery of orbit data . . . . . . . . . . . . . . . 7 4.1 Transaction Data Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

5

Description of Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1 5.2 5.3 5.4 Orbit File in ASCII Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Orbit Files Access Routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 ORBITA - File Read Routine Revolution Number File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Read Revolution Number File Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 DATREV - Revolution Number from Time 5.4.2 REVDAT - Perigee Times from Revolution Number Further Standard Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.1 GJ2EFS - convert geocentric position vector (J2000) to Earth-fixed 5.5.2 GEOLAT - get sub-satellite longitude, latitude and height Time Conversion Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.1 JD2000 - Convert Calendar Date to Modified Julian Date 2000 5.6.2 DJ2000 - Convert Modified Julian Date 2000 to Calendar Date Delivery Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 . . . . . . .11 11 . . . . . . .12 . . . . . . .13 13 14 . . . . . . .15 15 16 . . . . . . .17 17 18 . . . . . . .18

5.5

5.6

5.7


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References
Applicable Documents (AD):
AD.1 XMM Mission Implementation Plan XMM-MOC-PL-0100 Issue 0 (Draft): June 1995 XMM Mission Implementation Requirements Document PX-RS-0461 Issue 3.2: Septembre 1997 XMM Flight Dynamics Support Requirements Compilation XMM-MOC-RC-0001-OAD Issue 1.0 OAD Principles Standards for time and coordinate systems May 1994

AD.2

AD.3

AD.4

Reference Documents (RD):
RD.1 XMM FDS-XMCS File Transfer Mechanism ICD XMM-MOC-ICD-0018-DPD Issue TBD XMM Alternate Orbit with Apogee in the South MAS WP 391, G.Janin, Jan.1997 XMM: Optimisation of the Ground Station Visibility FDD WP 581, M. Rosengren, Sept. 1997 XMM ICD AMS Keyword Specifications for File Ingestion into AMS, XMM-SOC-ICD-0023-GC

RD.2 RD.3 RD.4


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XMM


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Glossary of Terms
A
ACAM AD AHF AMS AOCS AOS APES APF ASCII Assisted Circular Access Method Applicable Document Attitude History File Archive Management System; part of the XMM SOC Attitude and Orbit Control System Acquisition Of Signal Antenna Pointing Elements Attitude Parameter File American Standard Code for Information Interchange Beginning Of Life Attitude Constraint Checker Software. Provided by XFDS to SOC. Digital Audio Tape Dedicated Control Area Dedicated Control Room Declination; range -90 degrees ...+90 degrees ESOC's development LAN Data Processing Division (at ESOC) Database of Observable Bins. Provided by XFDS to SOC. Event Designator End Of Life European Photon Imaging Camera Enhanced Preferred Observation Sequence

FD FDD

FDCE FDR FDS FDDB FOP FOR FOV FSS FTP

B
BOL

Flight Dynamics Flight Dynamics Division (formerly known as OAD) also referred to as D/TOS-GSED/ FDD or GF Failure Detection and Correction Electronics Flight Dynamics Room Flight Dynamics (Support) System Flight Dynamics Database provided by DORNIER or MCSD Flight Operations Plan Frame of Reference Field Of View Fine Sun Sensor, optical sensor mounted along the S/C Z-axis File Transfer Protocol

C
CCHK

G H I
ICD ICS ICP ICV Interface Control Document Instrument Command Sequence Instrument Command Parameters; parameter file for the POS Intercenter Vector: tracking information to be provided to NASA stations International Gamma Ray Astrophysics Laboratory Immediate Parameter File Inertial Pointing and Slew mode (AOCS mode) Inertial Measurement Unit: a S/C rate sensor (like e.g. a gyro) Infrared Space Observatory Geocentric mean equatorial of epoch J2000.0 Local Area Network

D
DAT DCA DCR DEC DEVLAN DPD DBOB

INTEGRAL IPF IPS IMU ISO

E
ED EOL EPIC EPOS

J
J2000.0

L
LAN

F


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XSCS Orbit ICD - Glossary of Terms

LCT

LEOP LEOPOLD LIT LOS

Company which developed the LCT Ranging System, i.e. Laboratoire Central de Telecommunication, Velizy, France Launch and Early Orbit Phase Orbit determination facility Listen-In Test Loss Of Signal Main Control Room Mission Control Systems Division (formerly known as DPD) also referred to as D/TOS-GSED/ MCSD or GC Mission Implementation Plan Reaction Wheel Unit (RWU) momentum BIAS (activity) Mission Operation Centre Mission Operations Department (at ESOC) Message Out Multi Purpose Tracking System Multiple Satellite Support System - a predecessor of ORATOS Network Commanding, Telemetry and Ranging System: a Protocol Converter, part of the Mission Control System Orbit and Attitude Division (at ESOC), now called FDD On-Board Data Handling Operational Data Server Operational Flight Dynamics Database (optimised copy of the FDDB) Optical Monitor ESOC's operational LAN Orbit and Attitude Operations System

PMS PPF PSF POS

Payload Monitoring System (a part of the XMM XSCS) Pointing Properties File Planning Skeleton File Preferred Observation Schedule Quality Assurance Right Ascension; range 0 degrees ...+360 degrees Random Access Memory Reaction Control System Reference Document REmote Access to Circular History-files Re-planned EPOS Relative Pointing Error Re-planned POS Reaction Wheel Unit System Assurance Document Sun Acquisition Sensor Spacecraft Control and Operations System Star Catalogue Facility operational Spacecraft DataBase Science Operation Centre Spacecraft Operations Manager (MOD) Solar System Object Spacecraft Controller (MOD) Satellite Pointing Change Request Spacecraft Trajectory Data Messages Star Tracker System Validation Test To Be Confirmed To Be Decided TeleCommand

Q
QA

M
MCR MCSD

R
RA RAM RCS RD REACH REPOS RPE RPOS RWU

MIP MOBIAS MOC MOD MOUT MPTS MSSS

S
SAD SAS SCOS SCF SDB SOC SOM SSO SPACON SPCR STDM STR SVT

N
NCTRS

O
OAD OBDH ODS OFDDB

OM OPSLAN ORATOS

T
TBC TBD TC

P


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THR TM

Thruster TeleMetry User Requirements Document XMM Flight Dynamics System (developed by FDD) XMM Mission Control System (developed by MCSD) XMM Science Control System (developed by MCSD) X-Ray Multi Mirror

U
URD

X
XFDS XMCS XSCS XMM


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1

Introduction
The X-ray Multi Mirror (XMM) satellite is designed to observe the soft X-ray portion of the electromagnetic spectrum. It is planned to inject the satellite into an Earth orbit by an Ariane-5 launcher in August 1999. As a result of the mission analysis [RD.2], [RD.3] the following orbit type has been selected: height of perigee height of apogee semi-major axis eccentricity inclination arg. of perigee orbital period 7000 114100 66940 0.8005 40 50 47.87 degrees degrees hours km km km

In order to obtain good ground station coverage from Kourou, Fr. Guyana and Perth, Australia, a subsatellite longitude at apogee of about 90 degrees West (at beginning of life) was recommended in the above mentioned mission analysis work. Within this configuration the satellite can be tracked from ground for about 95% of the entire revolution. Of course, this orbit type with the desired subsatellite longitude at apogee will not be reached directly by the launcher. A few orbit correction manoeuvres will be required during the initial orbit phase in order to increase the perigee altitude from 600 km to about 7000 km and to reach the subsatellite longitude at apogee of about 90 degrees West. All the manoeuvres required for these orbit changes are planned to be carried out within the first few revolutions.


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XSCS Orbit ICD - Introduction


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2
2.1

Orbit Determination
XMM Orbit Determination
The orbit determination will be based on range and Doppler measurements from Kourou and Perth. The MPTS MKIII will be used for tracking and the performance is: · for range: bias of less than 20m including the various model errors; noise of less than 10m. · for Doppler: bias of less than 1 mm/s including the various model errors; noise of less than 2 mm/s It is assumed that tracking (range and Doppler) can be carried out without any restrictions during the entire passes. As the attitude control will be carried out through spinning wheels, momentum control will be required. Taking ISO as an example where momentum control is performed close to perigee, we experienced that the orbit determination had to be carried out primarily over 1.5 revolutions because of the difficulty in modelling the momentum control effect. The resulting error in the semi-major axis was about 50m. Considering the experience with ISO we took a somewhat pessimistic assumption for the XMM orbit determination accuracy, i.e. an error in the semi-major axis of a few hundred meters. Based on these figures the uncertainty in the propagation delay for all ground stations involved would be of the order of less than 30 microsec. It has to be mentioned, that this uncertainty is only valid for the first few days of the propagation period.

2.2

Orbit Determination Method
The orbit determination subsystem has to provide the satellite state (position and velocity) for the past and for the future. This information is required by the other subsystems of the Flight Dynamics area, and of course by other units outside Flight Dynamics, such as Spacecraft Operations, Ground Stations and Science Centres. Data closely related to the satellite motion, such as eclipse times and ground station visibility is also provided by the orbit determination subsystem. Very often the orbit determination is based on tracking measurements from various ground stations. The raw tracking measurements received from the ground stations are not directly suitable for orbit determination. In order not to overload the actual orbit determination with a large amount of measurements, a data reduction is required. The original raw tracking measurements are smoothed and a normal point is selected and kept as a so-called observation. The observations form the basis for the orbit determination. This is achieved by batch-wise processing of the observations using parameter estimation applying a least squares method. The orbit determination is performed in the following three steps: · Using an initial set of parameters, the assumed satellite motion is generated for the time interval of the selected observations;


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XSCS Orbit ICD - Orbit Determination

· ·

These generated satellite state vectors are compared with the actual observations and based on the differences resulting from this comparison, improvements to the initial set of parameters can be computed. This is performed by means of an iterative least squares approach.

The improved set of orbital parameters is essentially the output of this part. For fast and simple computation of the satellite state for any specific time it is essential to provide a routine which does not require the full orbit propagation method used before. For this reason the satellite movement, which has been determined within the above described method, is approximated 'piecewise' by a combination of a Kepler orbit and Chebyshev polynomials. The computed coefficients are stored on a data set, which permits easy and fast retrieval of the satellite state. Because only a small amount of data needs to be stored, the orbit file will contain data of the entire history, which is of high interest for evaluation and recomputation purposes. This orbit file constitutes the central place for the satellite state retrieval.


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3
3.1

Overview of Interfaces
List of tracking data input files
The interfaces are described in a separate ICD issued by GSED/MCSD. A summary will be given in the table below (not yet written) Description MPTS MkIII range MPTS MkIII Doppler MPTS MkIII meteo Antenna angles (plus meteorological data) Name Chapter Origin

3.2

List of interface files internal to Flight Dynamics
Description Momentum Control information Orbit manoeuvre input Orbit manoeuvre evaluation Name Chapter Subsystem

3.3

List of output files
As mentioned above the orbit determination subsystem produces the following output files: Description Orbit file related items: Orbit file for Flight Dynamics internal plus retrieval routine Orbit file for external interfaces (ASCII) plus retrieval routine propagation delay routine orbit ORBIT orbita ORBITA SIGDEL XMCS 5.1 XMCS XSCS FDS Name Chapter Destination


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XSCS Orbit ICD - Overview of Interfaces

Description Eclipse file Events file related items: Events file Revolution numbers plus retrieval routines

Name eclip

Chapter

Destination FDS

stef revno DATREV and REVDAT 5.3 5.4.1 and 5.4.2

FDS XSCS FDS

station predictions: (not yet written) STDM (possibly in two formats for STC I and for STC II) APES WIMPY XMCS XMCS XMCS

In addition to the various retrieval routines, some further standard routines will be delivered, which are listed under section "Further Standard Routines" at 5.5 and "Time Conversion Routines" at 5.6.


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4 Summary of XSCS interfaces and procedure for delivery of orbit data
The interfaces mentioned above with respect to XSCS are based on the requirements listed in the following documents: · Minutes of XMM MOC/SOC/FD meeting to discuss requirements on FD, 30.Oct.96 · Note on SOC requirements on DBOB generation, J.Riedinger, 8.Nov.96 · Note on XMM orbit interface for SOC, S.Pallaschke, 29.Jan.97 · Note on orbit file delivery, M.Merri, 6.May 97 It is envisaged to update the orbit file once per revolution in order to provide predictions with high accuracy. With this procedure the effect of the momentum control near perigee would always be taken into account in the generation of the predictions. The orbit file provided to XSCS via the ODF is an extract of the primary orbit file of the Flight Dynamics system and will contain only the current period, i.e. several weeks of history plus predictions of adequate duration. This orbit file contained within the ODF can be read using the retrieval routine ORBITA. In addition to this retrieval routine a further routine is made available which is required for the calculation of the subsatellite point and the altitude derived from the inertial spacecraft position.

4.1

Transaction Data Files
See [RD.4]


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5
5.1

Description of Interfaces
Orbit File in ASCII Format
The file is not intended for direct interpretation, but via access by the Fortran routine supplied. (See "ORBITA - File Read Routine" on page 11.) The content and format of the file is defined in the following tables. The format definition follows the ANSI FORTRAN notation for format statements (e.g. A29 means 29 ASCII characters, 5X means 5 spaces, I2 means a 2 character denary integer and F7.2 means a 7 character fixed point number with 2 decimal places). For each period of time there is a header block as shown in Table 1, followed by a number of polynomial coefficient blocks as shown in Table 2. The number of polynomial coefficient blocks depends upon the accuracy that is required. Name SCID Format I3,2X Description will contain the S/C body identification. The SCID is assigned before launch to the spacecraft, and remain the same throughout the mission. a single character flag indicating if the data is predicted (P) or reconstituted (R) date and time when the header block was written to the file in CCSDS time code A format (YYYYMM-DDThh:mm:ssZ) date and time of the start of the period for when the data is valid in CCSDS time code A format (YYYY-MM-DDThh:mm:ssZ). date and time of the end of the period for when the data is valid in CCSDS time code A format (YYYY-MM-DDThh:mm:ssZ). is a single line-feed character (ASCII 0A I3 F12.6 an internally used record identifier. Modified Julian Date 2000 (MJD 2000, i.e. the date 0.0 refers to the 1st January 2000 at 0:00:00), of the start of the period for when the data is valid. Modified Julian Date 2000 (MJD 2000), of the end of the period for when the data is valid. Modified Julian Date 2000 (MJD 2000), of the epoch for the reference Kepler orbit.
hex

PREREC GENTIM

A1,2X A20,2X

SRTTIM

A20,2X

ENDTIM

A20

LF NREC DAYBEG

)

DAYEND EPOCH

F12.6 F15.9


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XSCS Orbit ICD - Description of Interfaces

Name ORBIN SMAXIS OMOTIN

Format F11.3 F13.5 F13.5

Description Revolution number for this epoch. Semimajor axis 'a', in km, of the reference Kepler orbit. Inverse mean motion = 'a*sqrt(a/µ)' of the reference Kepler orbit in seconds/rad (µ = central Earth potential). is a single line-feed character (ASCII 0A
hex

LF NREC XYZPOS(3) XYZVEL(3) RDIST I3 3F11.3 3F11.7 F11.3

)

an internally used record identifier. are the x-y-z components of the position vector in km of the reference Kepler orbit. are the x-y-z components of the velocity vector in km/s of the reference Kepler orbit. is the absolute value of the position vector of the reference Kepler orbit in km.

Name NREC POLPOS(3) I3

Format

Description an internally used record identifier are the polynomial coefficients of the x-y-z components of the position vector in km of the reference Kepler orbit. are the polynomial coefficients of the x-y-z components of the velocity vector in km/s of the reference Kepler orbit.

3F11.3

POLVEL(3)

3F11.7

Depending upon the accuracy required the number of the coefficient blocks will vary between 0 and 10 inclusive The coordinate system is the Inertial Mean Geocentric Equatorial System of year J2000.0, with the x-axis towards the mean vernal equinox, the x-y plane coinciding with the mean equatorial plane and the z-axis toward north. Time and coordinate systems used for orbital operations at ESOC are described in "OAD Principles, Standards for time and coordinate systems, May 1994".


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5.2
5.2.1

Orbit Files Access Routine
ORBITA - File Read Routine
The orbit file can be read by a FORTRAN subroutine. The calling sequence is shown below.

5.2.1.1

Synopsis
SUBROUTINE ORBITA (MJDATE, CODE, FILE-UNIT, IERROR, SATNUM, X, REVNUM)

5.2.1.2

Input
Parameter DOUBLE PRECISION MJDATE Description Requested epoch in MJD-2000. See "JD2000 - Convert Calendar Date to Modified Julian Date 2000" on page 17. Number of components desired of state vector dimension of array X(); 3: S/C position; 6: position and velocity Logical Fortran Unit number of orbit file

INTEGER

a

CODE

INTEGER FILE-UNIT

a. In this document, it is assumed that all integers are 4-byte integers.

5.2.1.3

Output
Parameter INTEGER IERROR INTEGER SATNUM DOUBLE PRECISION X(CODE) DOUBLE PRECISION REVNUM Description Error code See "Return" on page 11. Satellite number spacecraft position [km] (and velocity [km/ s]) revolution number; Note: this is a DOUBLE PRECISION! - do not confuse with "DATREV - Revolution Number from Time" at 5.4.1

5.2.1.4

Return


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ORBITA returns return one of the following return codes: Return Code
0 1

Description no error MJDATE is too early (outside the interval for which orbit information is available) MJDATE is too late (outside the interval for which orbit information is available) wrong value of `CODE' `FILE-UNIT' out of range [<1] read error from compressed orbit file compressed orbit file content is inconsistent

2

3 4 6 7

5.2.1.5

Description
For reading an orbit file, the User must assign a FORTRAN IO unit number to it. This FORTRAN IO unit number shall be used for the parameter FILE-UNIT, and the satellite number is returned as the parameter SATNUM. By verifying the latter, the User can check that a block from the correct orbit file has been read. The subroutine ORBITA does not explicitly open the orbit file. At the first call of the subroutine ORBITA, the orbit file is read from the beginning until a block is found whose time interval contains the input value MJDATE. In case there is some time overlap between blocks, the first one that contains MJDATE is selected. After a block is found, the decompressing is performed as described below. The content of the block is kept inside the subroutine and is reused at the next call of ORBITA, if the new value of MJDATE lies within its time interval. If the new MJDATE lies beyond the end of the interval, the orbit file is read forward until a matching interval is found. The orbit file is read from its beginning at a new call of ORBITA when: · The new value of MJDATE lies before the start time of the interval for the last read block; · The error return code IERROR was non-zero at the last call; · The new call specifies a new file with a new number FILE-UNIT. · An update of the orbit file was made between reads.

5.3

Revolution Number File
The file has the name revno and contains the information of the perigee times and the


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associated revolution numbers. The file is updated at the time when the orbit events are calculated. However, this revolution number file provides the entire history of the mission form launch onwards plus the requested predictions, whereas the orbit events file only contains the information of the current period.

5.4

Read Revolution Number File Routines
Two routines will be provided either to retrieve the revolution number corresponding to a given time or to retrieve the time interval for a given revolution number.

5.4.1
5.4.1.1

DATREV - Revolution Number from Time
Synopsis
SUBROUTINE DATREV (FILE-UNIT, MJDATE, NUMREV, TS, TE, IERROR)

5.4.1.2

Input
Parameter INTEGER FILE-UNIT DOUBLE PRECISION MJDATE Description Logical number of input data file Input from Date page date expressed as Modified Julian day, 2000. See "JD2000 - Convert Calendar to Modified Julian Date 2000" on 17.

5.4.1.3

Output
Parameter INTEGER NUMREV DOUBLE PRECISION TS Description Revolution number start time (true anomaly = 0 degrees) of revolution NUMREV expressed as Modified Julian day, from 2000 end time (true anomaly = 360 degrees) of revolution NUMREV expressed as Modified Julian day, from 2000 Return code

DOUBLE PRECISION TE

INTEGER IERROR


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XSCS Orbit ICD - Description of Interfaces

5.4.1.4

Return
Return Code 0 1 2
4 6 7

Description no error MJDATE is too early (outside the interval for which orbit information is available) MJDATE is too late (outside the interval for which orbit information is available) `FILE-UNIT' out of range [<1] read error from revolution number file revolution number file content is inconsistent

5.4.1.5

Description
DATREV retrieves the revolution number as well as its start- and end-date for a given time.

5.4.2
5.4.2.1

REVDAT - Perigee Times from Revolution Number
Synopsis
SUBROUTINE REVDAT (FILE-UNIT, NUMREV, TS, TE, IERROR)

5.4.2.2

Input
Parameter INTEGER FILE-UNIT INTEGER NUMREV Description Logical number of input data file Revolution number

5.4.2.3

Output
Parameter DOUBLE PRECISION TS Description start time (true anomaly = 0 degrees) of revolution NUMREV expressed as Modified Julian day, from 2000. See "DJ2000 - Convert Modified Julian Date 2000 to Calendar Date" on page 18.


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Parameter DOUBLE PRECISION TE

Description end time (true anomaly = 360 degrees) of revolution NUMREV expressed as Modified Julian day, from 2000. See "DJ2000 - Convert Modified Julian Date 2000 to Calendar Date" on page 18. Return code

INTEGER IERROR

5.4.2.4

Return
Return Code 0 1 2
4 6 7

Description no error `NUMREV' too small (outside the interval for which orbit information is available) `NUMREV' too large (outside the interval for which orbit information is available) `FILE-UNIT' out of range [<1] read error from revolution number file revolution number file content is inconsistent

5.4.2.5

Description
REVDAT retrieves the start and end date for a given revolution number.

5.5

Further Standard Routines
As mentioned above some further routines from the standard orbit provided for the calculation of the subsatellite point using the routine this routine requires as input the satellite position vector in the Earth system, another routine has to be called before which converts retrieved through the routine ORBITA from the J2000 system to the libraries will be GEOLAT. Since fixed coordinate the state vector Earth Fixed one.

5.5.1
5.5.1.1

GJ2EFS - convert geocentric position vector (J2000) to Earth-fixed
Synopsis
SUBROUTINE GJ2EFS (MJDATE, XJ2000, XEFS)


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5.5.1.2

Input
Parameter DOUBLE PRECISION MJDATE Input from Date page Description date expressed as Modified Julian day, 2000. See "JD2000 - Convert Calendar to Modified Julian Date 2000" on 17.

DOUBLE PRECISION XJ2000(3)

Spacecraft position vector in the J2000 system; [X, Y, Z in km]

5.5.1.3

Output
Parameter DOUBLE PRECISION XEFS(3) Description position vector in the Earth-fixed system (see [AD.4])

5.5.1.4

Return
GJ2EFS does not return any codes

5.5.1.5

Description
GJ2EFS converts a position vector conversion from geocentric J2000 to Earth-fixed system.

5.5.2
5.5.2.1

GEOLAT - get sub-satellite longitude, latitude and height
Synopsis
SUBROUTINE GEOLAT (X, LONGITUDE, LATITUDE, HEIGHT)

5.5.2.2

Input
Parameter DOUBLE PRECISION X(3) Description Spacecraft position vector in earth-fixed system (see [AD.4]); [X, Y, Z in km]

5.5.2.3

Output
Parameter DOUBLE PRECISION LONGITUDE Description sub-satellite longitude (in radians)


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Parameter DOUBLE PRECISION LATITUDE DOUBLE PRECISION HEIGHT

Description sub-satellite latitude (in radians) height above the Earth in km

5.5.2.4

Return
GEOLAT does not return any codes

5.5.2.5

Description
GEOLAT calculates sub-satellite longitude and latitude and the height above the Earth form an Earth-fixed position vector.

5.6
5.6.1
5.6.1.1

Time Conversion Routines
JD2000 - Convert Calendar Date to Modified Julian Date 2000
Synopsis
SUBROUTINE JD2000 (MJDATE, YEAR, MONTH, DAY, HOUR, MINUTE, SECOND)

5.6.1.2

Input
Parameter INTEGER YEAR INTEGER MONTH INTEGER DAY INTEGER HOUR INTEGER MINUTE DOUBLE PRECISION SECOND Description Year A.D.; e.g. 1999 Month of the year; 1 ... 12 Day of the month; 1 ... 28, 29, 30, 31 Hour of the day; 0 ... 23 Minute of the hour; 0 ... 59 Second of the minute; 0.0 ... 59.999...

5.6.1.3

Output
Parameter DOUBLE PRECISION MJDATE Description Modified Julian Date 2000

5.6.1.4

Return


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JD2000 does not return any codes

5.6.1.5

Description
JD2000 calculates Modified Julian Date (MJD2000) from calendar date.

5.6.2
5.6.2.1

DJ2000 - Convert Modified Julian Date 2000 to Calendar Date
Synopsis
SUBROUTINE JD2000 (MJDATE, YEAR, MONTH, DAY, HOUR, MINUTE, SECOND)

5.6.2.2

Input
Parameter DOUBLE PRECISION MJDATE Description Modified Julian Date 2000

5.6.2.3

Output
Parameter INTEGER YEAR INTEGER MONTH INTEGER DAY INTEGER HOUR INTEGER MINUTE DOUBLE PRECISION SECOND Description Year A.D.; e.g. 1999 Month of the year; 1 ... 12 Day of the month; 1 ... 28, 29, 30, 31 Hour of the day; 0 ... 23 Minute of the hour; 0 ... 59 Second of the minute; 0.0 ... 59.999...

5.6.2.4

Return
JD2000 does not return any codes

5.6.2.5

Description
JD2000 calculates calendar date from Modified Julian Date (MJD2000).

5.7

Delivery Mechanism
The following routines are delivered as FORTRAN 77 source code files: · ORBITA - File Read Routine · DATREV - Revolution Number from Time


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· · · · ·

REVDAT - Perigee Times from Revolution Number GJ2EFS - convert geocentric position vector (J2000) to Earth-fixed GEOLAT - get sub-satellite longitude, latitude and height JD2000 - Convert Calendar Date to Modified Julian Date 2000 DJ2000 - Convert Modified Julian Date 2000 to Calendar Date


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XSCS Orbit ICD - Description of Interfaces