| Earth Observation Mission CFI Software Lib Software User Manual |

Earth Observation Mission CFI Software
LIB SOFTWARE USER MANUAL

Code | EO-MA-DMS-GS-013
Issue | 4.4
Date | 05/07/12

| Name | Function | Signature
Prepared by: | Carlos Villanueva Muñoz | Project Manager |
Checked by: | Carlos Villanueva Muñoz | Project Manager |
Approved by: | José Antonio González Abeytua | Division Head |

# DOCUMENT INFORMATION

Contract Data | Classification
--- | ---
Contract Number: | 15583/01/NL/GS | Internal |
Public |
Contract Issuer: | ESA / ESTEC | Industry | X
Confidential |

External Distribution
Name | Organization | Copies

Electronic handling
Document generator: | Doxygen 1.7.1
Electronic file name: | eo-ma-dms-gs-013-10

# Document Status Log

Issue | Change Description | Date | Approval
--- | --- | --- | ---
1.0 | First release These libraries corresponds to version 4.0 of C libraries. | 27/03/09 |
4.1 | Second release - Issue in line with C version These libraries corresponds to version 4.1 of C libraries. | 07/05/10 |
4.2 | Third release These libraries corresponds to version 4.2 of C libraries. | 31/01/11 |
4.3 | Fourth release These libraries corresponds to version 4.3 of C libraries. | 06/02/12 |
4.4 | Fifth release These libraries corresponds to version 4.4 of C libraries. | 05/07/12 |

# ACRONYMS, NOMENCLATURE AND TERMINOLOGY

## Acronyms

ANX | Ascending Node Crossing
AOCS | Attitude and Orbit Control Subsystem
ASCII | American Standard Code for Information Interchange
BOM | Beginning Of Mission
CFI | Customer Furnished Item
EOM | End Of Mission
ESA | European Space Agency
ESTEC | European Space Technology and Research Centre
GPL | GNU Public License
GPS | Global Positioning System
IERS | International Earth Rotation Service
I/F | Interface
LS | Leap Second
OBT | On-board Binary Time
OSF | Orbit Scenario File
SRAR | Satellite Relative Actual Reference
SUM | Software User Manual
TAI | International Atomic Time
UTC | Coordinated Universal Time
UT1 | Universal Time UT1
WGS[84 | World Geodetic System 1984

## Nomenclature

CFI | A group of CFI functions, and related software and documentation. that will be distributed by ESA to the users as an independent unit
CFI function | A single function within a CFI that can be called by the user
Library | A software library containing all the CFI functions included within a CFI plus the supporting functions used by those CFI functions (transparently to the user)

## Notes in Terminology

In order to keep compatibility with legacy CFI libraries, the Earth Observation Mission CFI Software makes use of terms that are linked with missions already or soon in the operational phase like the Earth Explorers. This may be reflected in the rest of the document when examples of Mission CFI Software usage are proposed or description of Mission Files is given.

# APPLICABLE AND REFERENCE DOCUMENTS

## Applicable Documents

[GEN_SUM] | Earth Observation Mission CFI Software. General Software User Manual. EO-MA-DMS-GS-017. Issue 4.4 05/07/12

## Reference Documents

[MCD] | Earth Observation Mission CFI Software. Conventions Document. EO-MA-DMS-GS-0001. Issue 4.4 05/07/12.
[MSC] | Earth Observation Mission CFI Software. Mission Specific Customizations. EO-MA-DMS-GS-0018. Issue 4.4 05/07/12.
[EE_COMMON_SUM] | Earth Observation Mission CFI Software. EECommon Software User Manual. EO-MA-DMS-GS-010. Issue 4.4 05/07/12.
[F_H_SUM] | Earth Observation Mission CFI Software. FileHandling Software User Manual. EO-MA-DMS-GS-011. Issue 4.4 05/07/12.
[D_H_SUM] | Earth Observation Mission CFI Software. DataHandling Software User Manual. EO-MA-DMS-GS-012. Issue 4.4 05/07/12.
[IERS] | http://www.iers.org/iers/publications/bulletins/

# INTRODUCTION

## Classes Overview

This software library contains all low-level generic routines, supporting all the other CFI functions. The following CFI classes are included:

- AeolusObt: Class for Aeolus on-board time.
- CfiId: Base class for CFI Id objects.
- Coord: Class to store coordinates.
- Time (defined in EETime.h): Class for time operations.
- EnvisatObt: Class for Envisat on-board time.
- Geodetic: Class for geodetic coordinates.
- GoceObt: Class for GOCE on-board time.
- LibFunc: Class with several algebraic operations in static methods.
- ModelId: Class for Model Id.
- ObtTime: Base class for on-board time classes.
- SatId: Class for Satellite Id.
- SmosObt: Class for SMOS on-board time.
- StarData (defined in Star.h): Class for operations with Stars.
- StateVector: Class to store Orbit State Vector.
- TimeCorrelation: Class for Time Id.

The following auxiliary classes are also included (in LibData.h):

- Kepler: Class defining keplerian elements.
- LeapSecondInfo: Class defining leap second information.
- ModelData: Class for model data.
- OrbitInterval: Class defining am orbit interval.
- TimeCorrelationData: Class defining timeCorrelations.
- TimeData: Class defining reference time relations.
- TimeInterval: Class defining a time interval.
- Topocentric: Class for topocentric coordinates.

## TIME COMPUTATIONS

All time time computations are peformed internally using the continuous TAI time reference. Therefore the input and output parameters are converted internally to the adequate time reference.

### Time Reference Transformations Initialization

- TimeCorrelation::TimeCorrelation: constructor that initialize time correlations between TAI, UTC, UT1 and GPS times from:
  - reference data files.
  - input reference times.
- TimeCorrelation::getLeapSecondInfo: retrieves the leap second location (if any) in the initialised time range.

### Time Format and Reference Transformations, operations between dates

- Time::setAscii: transforms a time expressed in a given ASCII format and reference (TAI, UTC, UT1 or GPS) into a time in Processing format, performing a reference transformation if necessary (to TAI, UTC, UT1 or GPS), and storing the result in the object.
- Time::getAscii: transforms the time stored in the object, expressed in Processing format and a given reference (TAI, UTC, UT1 or GPS), into a time in an ASCII format, performing a reference transformation if necessary (to TAI, UTC, UT1 or GPS).
- Time::getTransport: transforms the time stored in the object, expressed in Processing format and a given reference (TAI, UTC, UT1 or GPS) into a time in a Transport format, performing a reference transformation if necessary (to TAI, UTC, UT1 or GPS).
- Time::getProcessing and Time::change: transforms a time expressed in Processing format and a given reference (TAI, UTC, UT1 or GPS) into a time in Processing format with a different reference (TAI, UTC, UT1 or GPS).
- Time::setTransport: transforms a time expressed in a given Transport format and reference (TAI, UTC, UT1 or GPS) into a time in Processing format, performing a reference transformation if necessary (to TAI, UTC, UT1 or GPS),and storing result in object.

### Operation between Dates

- Time::operator+: adds a duration to time stored in Time object.
- Time::operator-: subtracts a duration to time stored in Time object / subtracts two Time objects.

### Transformations from/to On-board Times

Operations with On-board times are done with the class corresponding with the satellite being studied: AeolusObt, EnvisatObt, GoceObt, SmosObt. Each one has the following methods:

- getTime: transforms the On-board Time (OBT) stored in the corresponding object into a Time object.
- setTime: set the OBT of the object transforming the processing time stored in a Time object.

## COORDINATE SYSTEMS TRANSFORMATIONS

### Reference Frames Transformations

- StateVector::change: transforms a state vector between different coordinate systems.
- Coord::topocentricToEf: transforms a state vector from topocentric coordinates to the Earth Fixed CS.
- Coord::efToTopocentric: transforms a state vector from the Earth Fixed CS to topocentric coordinates.

### Attitude-related Computations

- LibFunc::eulerToMatrix: computes the elements of the coordinate transformation matrix with respect to the attitude frame given the corresponding Euler rotation vector in the roll, pitch and yaw sequence.
- LibFunc::matrixToEuler: derives the Euler rotation vector with respect to the attitude frame in the roll, pitch and yaw sequence given the corresponding coordinate transformation matrix.
- LibFunc::getRotationAngles: calculates the rotation angles between two sets of orthonormal right-handed unit vectors expressed wrt an identical coordinate frame.
- LibFunc::getRotatedVector: calculates the rotated unit vectors given a set of unit vectors and the rotation angles expressed wrt an identical coordinate frame.
- LibFunc::quaternionsToVectors: calculates the orthonormal unit vectors from a given set of quaternions.
- LibFunc::vectorsToQuaternions: calculates the set of quaternions that correspond to a set of orthonormal unit vectors.

### Coordinates Transformations

- Coord::setGeodetic: transforms from Geodetic to Cartesian coordinates.
- Coord::getGeodetic: transforms from Cartesian to Geodetic coordinates.
- Coord::getRaDec: transforms from a cartesian vector to right ascension and declination.
- StarData::getCart: transforms from right ascension and declination to a cartesian vector.

### State Vector Transformations

- Coord::setKepler: transforms from Keplerian to Cartesian coordinates.
- Coord::getKepler: transforms from Cartesian to Keplerian coordinates.

### Position on orbit calculations

- StateVector::getPositionOnOrbit: calculates a value describing the position of the satellite within the orbit, using as input a Cartesian orbit state vector.

## Other Basic Computations

- StateVector::setSun: calculates the position and velocity of the Sun in the Earth Fixed coordinate system
- StateVector::setMoon: calculates the Moon position and velocity in the Earth Fixed coordinate system
- StateVector::setPlanet: calculates the position and velocity of a selected planet in the Earth Fixed coordinate system
- StarData::getStar: calculates the right ascension and declination of a star in the True of Date coordinate system.
- StarData::changeCatalog: calculates the star coordinates in a star catalogue reference frame.
- Geodetic::geoDistance: calculates the geodesic distance between two points that lay on the same ellipsoid, and the azimuth of the related geodesic line at both points.

## Astronomical model selection

Models can be initialized using the Model class and its methods.

# Time Reference Transformations Calling Sequence

Time reference transformations, and other functions with time as input, requires the user to initialise correlations between the different allowed time references, i.e. TAI, UTC, UT1 and GPS time. This can be done using the constructors of the Time class. Once the initialisation has been performed, the user is able to transform any date expressed in one of the allowed time references to another, through the methods in Time class. A Time object must be initialized with the TimeCorrelation object previously created, and its methods provide the trasnformations. A complete view of the time reference transformations sequence is presented in following figure:

Please refer also to:

- [MCD] for a detailed description of the time references and formats, coordinate systems, parameters and models used in this document.
- [GEN_SUM] for a complete overview of the CFI, and in particular the detailed description of the Id concept and the error handling functions.

# Earth and Astronomical model selection calling sequence

The CFI functions can work with different Earth and astronomical models. These models have been divided in the following categories:

- Star model
- Sun model
- Planet model
- Earth model
- Moon model
- Nutation model
- Precession model
- Constants model

In order to work with different models, these have to be stored in a CFI Id called Model ID. The Model ID is an object of type ModelId. The calling sequence for a C program where the Model ID is needed, would be as follows:

- Create the modelId object: ModelId modelId;
- Optionally, initialise the modelId with ModelId::init method. This method would set the requested models in the modelId. Note that if the modelId is not initialised this way, the Earth Observation CFI functions will use the default models.
- The modelId is used as an input parameter in the Earth Observation CFI methods if it is needed.

Please refer also to:

- [MCD] for a detailed description of the models implemented for the Earth Observation CFI. (For the current version, only the default models are available)
- [GEN_SUM] for a detailed description of the Id concept.

# LIBRARY INSTALLATION

For a detailed description of the installation of any CFI library, please refer to [GEN_SUM].

# LIBRARY USAGE

Note that to use the CFI LIB software library, the following other CFI software libraries are required:

- EE_COMMON
- FILE_HANDLING
- DATA_HANDLING

It is needed to have properly installed in the system the following external GPL library:

- LIBXML2 (MIT license, see [GEN_SUM])
- POSIX thread library: libpthread.so (pthread.lib for WINDOWS, with license LGPL)

To use the CFI LIB software library in an user application, that application must include in its source code the header files where the classes that are going to be used are defined.
To link correctly this application, the user must include in his linking command flags like (assuming cfi_lib_dir and cfi_include_dir are the directories where respectively all CFI libraries and include files have been installed, see [GEN_SUM] for installation procedures):

- LINUX:
  -Icfi_include_dir -Lcfi_lib_dir
  -lCfiLib -lCfiDataHandling -lCfiFileHandling -lCfiEECommon -lxml2 -lpthread
- MacOS:
  -Icfi_include_dir -Lcfi_lib_dir
  -lCfiLib -lCfiDataHandling -lCfiFileHandling -lCfiEECommon -lpthread
  -framework libxml
- WINDOWS (dynamic libraries):
  /I "cfi_include_dir" /libpath:"cfi_lib_dir"
  libCfiLib.lib libCfiDataHandling.lib libCfiFileHandling.lib libCfiEECommon.lib
- WINDOWS (static libraries):
  /I "cfi_include_dir" /libpath:"cfi_lib_dir"
  libCfiLib.lib libCfiDataHandling.lib libCfiFileHandling.lib libCfiEECommon.lib libxml2.lib pthread.lib

Note that, as Earth Observation CFI libraries are dynamic, cfi_lib_dir must be included in the path where the system looks for dynamic libraries (LD_LIBRARY_PATH in LINUX, DYLD_LIBRARY_PATH in MacOs). For WINDOWS sytem, the executable will look for .dll libraries, not the .lib ones that are used to create the executable, so they must be in the path described by PATH variable.
All the classes described in this document are defined in EECFI namespace, to avoid any possible conflict with classes of other libraries, so the user must choose one of the following two options in order to use the classes:

- Inserting using namespace EECFI; in the code.
- Using the classes with the namespace prefix (e.g.: EECFI::OrbitFile orbitFile;)

# ERROR HANDLING

The error management in C++ LIB is made throw exceptions, that is, if any error is produced, an exception of type CfiError is thrown and it must be catched putting the code inside a try-catch block.
See [GEN_SUM] to know more about how to handle the CFI errors. For a descripton about the CfiError class and its methods, see [EE_COMMON_SUM].