YOIFITS

This project provides support for OI-FITS (optical interferometry data format) in Yorick.

Installation is explained below.

Usage

If properly installed, the software exploits the auto-load facility of Yorick so that there are no needs to #include "oifits.i".

Dealing with an existing OI-FITS file

First, load OI-FITS data from a file:

ws = oifits_load(filename);

where ws is the handle to manipulate the contents of the OI-FITS file and filename is the name of the OI-FITS file.

OI-FITS data is stored in a collection of FITS header data units (HDU). This structure is reproduced by the plugin where a data-block correspond to a FITS HDU. In order to access the OI-FITS contents, you have to select a specific data-block. For instance, you can loop over all the data-blocks of the handle ws with:

for (db = oifits_first(ws); db; db = oifits_next(ws, db)) {
    ...;
}

where db is another kind of handle but to a specific data-block this time.

In the loop, the function oifits_is_data can be used to check whether a given data-block contains interferometric data (true for OI_VIS, OI_VIS2 and OI_T3 data-blocks).

There are many functions to access the contents of a given data-block. Again, the OI-FITS structure of a HDU is reproduced and the general syntax to query a specific field is:

oifits_get_FIELDNAME(ws, db);

where FIELDNAME is the name of the OI-FITS field which is the same as the corresponding FITS keyword or column in lowercase letters and with non alphanumerical characters replaced by an underscore _. For instance, to query the effective wavelength, just do:

oifits_get_eff_wave(ws, db);

where db is an OI_WAVELENGTH, OI_VIS, OI_VIS2 or OI_T3 data-block of OI-FITS instance ws. The reasons that you have to provide both ws and db are that some information (as the effective wavelength) of the data-block db may be stored in an other data-block of the same OI-FITS instance ws and Yorick does not allow circular references.

The following is applicable to all data-blocks:

• oifits_get_revn: get revision number of the table definition

To query the fields of OI_VIS, OI_VIS2 or OI_T3 data-blocks:

• oifits_get_date_obs: get UTC start date of observations
• oifits_get_time: get UTC time of observation (s)
• oifits_get_mjd: get Modified Julian Date
• oifits_get_int_time: get integration time (s)
• oifits_get_sta_index: get station numbers contributing to the data
• oifits_get_flag: get flags
• oifits_get_visamp: get visibility amplitude
• oifits_get_visamperr: get error in visibility amplitude
• oifits_get_visphi: get visibility phase (deg)
• oifits_get_visphierr: get error in visibility phase (deg)
• oifits_get_vis2data: get squared visibility
• oifits_get_vis2err: get error in squared visibility
• oifits_get_t3amp: get triple-product amplitude
• oifits_get_t3amperr: get error in triple product amplitude
• oifits_get_t3phi: get triple-product phase (deg)
• oifits_get_t3phierr: get error in triple product phase (deg)
• oifits_get_ucoord: get u coordinate of the data (m)
• oifits_get_vcoord: get v coordinate of the data (m)
• oifits_get_u1coord: get u coordinate of baseline AB of the triangle (m)
• oifits_get_v1coord: get v coordinate of baseline AB of the triangle (m)
• oifits_get_u2coord: get u coordinate of baseline BC of the triangle (m)
• oifits_get_v2coord: get v coordinate of baseline BC of the triangle (m)

To query fields of OI_ARRAY data block:

• oifits_get_arrname: get identifier of corresponding OI_ARRAY
• oifits_get_frame: get coordinate frame
• oifits_get_arrayx: get X coordinate of array center (m)
• oifits_get_arrayy: get Y coordinate of array center (m)
• oifits_get_arrayz: get Z coordinate of array center (m)
• oifits_get_tel_name: get telescope name
• oifits_get_sta_name: get station name
• oifits_get_sta_index: get station number
• oifits_get_diameter: get element diameter (m)
• oifits_get_staxyz: get station coordinate relative to array center (m)

To query fields of OI_TARGET data block:

• oifits_get_target_id: get index number of target(s)
• oifits_get_target: get target names(s)
• oifits_get_raep0: get R.A. at mean equinox (deg)
• oifits_get_decep0: get decl. at mean equinox (deg)
• oifits_get_equinox: get equinox
• oifits_get_ra_err: get error in R.A. at mean equinox (deg)
• oifits_get_dec_err: get error in decl. at mean equinox (deg)
• oifits_get_sysvel: get Systemic radial velocity (m/s)
• oifits_get_veltyp: get reference for radial velocity ("LSR", "GEOCENTR", etc.)
• oifits_get_veldef: get definition of radial velocity ("OPTICAL", "RADIO")
• oifits_get_pmra: get proper motion in R.A. (deg/yr)
• oifits_get_pmdec: get proper motion in decl. (deg/yr)
• oifits_get_pmra_err: get error of proper motion in R.A. (deg/yr)
• oifits_get_pmdec_err: get error of proper motion in decl. (deg/yr)
• oifits_get_parallax: get parallax (deg)
• oifits_get_para_err: get error in parallax (deg)
• oifits_get_spectyp: get spectral type

To query fields of OI_WAVELENGTH data block:

• oifits_get_insname: get identifier of corresponding OI_WAVELENGTH
• oifits_get_eff_wave: get effective wavelength of channel (m)
• oifits_get_eff_band: get effective bandpass of channel (m)

Creating a new OI-FITS file

In order to create a new OI-FITS file, you first create a new OI-FITS handle in Yorick, then you populate it with data-blocks and, finally, you save it to the disk.

To create a new OI-FITS instance:

ws = oifits_new();

To add data-blocks:

oifits_insert, ws, db1, db2, ...;

where db1, db2, etc. are OI-FITS data-blocks which have been freshly created (see below) or which are borrowed from another OI-FITS instance.

To create a new data-block, the general syntax is:

db = oifits_new_DBTYPE(key1=val1, key2=val2, ...);

where DBTYPE is the data-block type (target, array, wavelength, spectrum, vis, vis2 or t3) and all fields of the data-block are passed by keyword. Note that all fields must be specified. See the individual documentation of the data-block constructors to figure out which fields are required. For instance:

help, oifits_new_vis2;

Optionally, the OI-FITS instance to which insert the new data-block can be specified in a data-block constructor:

oifits_new_DBTYPE, ws, key1=val1, key2=val2, ...;

is the same as:

oifits_insert, ws, oifits_new_DBTYPE(key1=val1, key2=val2, ...);

There may be any number of data-blocks in an OI-FITS instance and they may be inserted at any time and in any order. After inserting the data-blocks, it is necessary to make sure that the internals of the OI-FITS instance are consistent (otherwise some functionalities may not work as expected). Updating internal information is done by:

oifits_update, ws;

Saving an OI-FITS instance to a file is as simple as:

oifits_save, ws, filename;

where filename is the name of the OI-FITS file. The oifits_save subroutine has a number of keywords to add comments, history records or to allow overwritting an existing file (which is forbidden by default).

Simulated Data

If the contents of an OI-FITS data-block correspond to model data, you may simulate additive noise with:

out = oifits_add_noise(ws, method, level);

which has the effect of adding noise to all OI_VIS, OI_VIS2 or OI_T3 data-blocks of the OI-FITS instance ws and returns a new OI-FITS instance. The other arguments are as follows:

• method = 1 or "generate" to add noise to noiseless data; the standard deviation of the noise is taken from the contents of ws; in this case, the level argument must be undefined or omitted.

• method = 2 or "snr" to add noise to noiseless data; the standard deviation of noise is computed to achieve a signal-to-noise ratio equal to the value of level.

• method = 3 or "amplify" to add noise to noisy data so that the standard deviation of total noise (existing one plus added one) is multiplied by the value of level which must be greater or equal one. The standard deviation of the noise prior to the amplification is taken from the contents of ws.

The operation can also be carried out in-place by calling oifits_add_noise as a subroutine:

oifits_add_noise, ws, method, level;

Installation

Installation with EasyYorick

Installation of YOIFITS by EasyYorick is fully supported. Assuming you have installed EasyYorick, you just have to execute:

ypkg install yorick yeti yoifits

which should install Yorick, Yeti (if not yet installed) and YOIFITS.

To upgrade to the last master version:

ypkg upgrade yoifits

Manual installation

1. You must have Yorick and Yeti installed on your machine.

2. Unpack the software code somewhere or clone the Git repository:

   git clone https://github.com/emmt/YOIFITS.git yoifits

   if you want/prefer to use HTTPS, or:

   git clone git@github.com:emmt/YOIFITS.git yoifits

   if you want/prefer to use SSH. Any of these commands creates a local GIT repository named yoifits.

3. Configure for compilation. There are two possibilities (the first one is recommended):

   • For an out-of-place build, create a dedicated build directory, say $BUILD_DIR, go to the build directory and run the configuration script:

     mkdir -p $BUILD_DIR
     cd $BUILD_DIR
     $SRC_DIR/configure

     where $SRC_DIR is the path to the source directory of the plug-in code. To see the configuration options, type:

     $SRC_DIR/configure --help

   • For an in-place build, go to the source directory, say $SRC_DIR, of the plug-in code and run the configuration script:

     cd $SRC_DIR
     ./configure

     To see the configuration options, type:

     ./configure --help

4. Compile the code:

   make clean
   make

5. Install YOIFITS (you must have write access granted to Yorick directories):

   make install