sora.observer

The Observer Class

class sora.Observer(**kwargs)[source]

Defines the observer object.

name

Name for the Observer. Observer is uniquely defined (name must be different for each observer).

Type: str

code

The IAU code for SORA to search for its coordinates in MPC database.

Type: str

site

User provides an EarthLocation object.

Type: astropy.coordinates.EarthLocation

lon

The Longitude of the site in degrees. Positive to East. Range (0 to 360) or (-180 to +180). User can provide in degrees (float) or hexadecimal (string).

Type: str, float

lat

The Latitude of the site in degrees. Positive North. Range (+90 to -90). User can provide in degrees (float) or hexadecimal (string).

Type: str, float

height

The height of the site in meters above see level.

Type: int, float

ephem

The ephemeris used to locate the observer on space. It can be “horizons” to use horizons or a list of kernels

Type: str, list

Examples

User can provide one of the following to define an observer:

If user will use the MPC name for the site:

>>> Observer(code)

If user wants to use a different name from the MPC database:

>>> Observer(name, code)

If user wants to use an EarthLocation value:

>>> from astropy.coordinates import EarthLocation
>>> EarthLocation(lon, lat, height)
>>> Observer(name, site)

If user wants to give site coordinates directly:

>>> Observer(name, lon, lat, height)

altaz(time, coord)[source]

Calculates the Altitude and Azimuth at a reference time for a coordinate.

Parameters

time (str, astropy.time.Time) – Reference time to calculate the sidereal time. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.
coord (str, astropy.coordinates.SkyCoord) – Coordinate of the target ICRS.

Returns

altitude (float) – Object altitude in degrees.
azimuth (float) – Object azimuth in degrees.

get_ksi_eta(time, star)[source]

Calculates relative position to star in the orthographic projection.

Parameters

time (str, astropy.time.Time) – Reference time to calculate the position. It can be a string in the format 'yyyy-mm-dd hh:mm:ss.s' or an astropy Time object.
star (str, astropy.coordinates.SkyCoord) – The coordinate of the star in the same reference frame as the ephemeris. It can be a string in the format 'hh mm ss.s +dd mm ss.ss' or an astropy SkyCoord object.

Returns

ksi, eta – On-sky orthographic projection of the observer relative to a star. ksi is in the North-South direction (North positive). eta is in the East-West direction (East positive).

Return type

float

get_vector(time, origin='barycenter')[source]

Return the vector Origin -> Observer in the ICRS

Parameters

time (str, astropy.time.Time) – Reference time to calculate the object position. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.
origin (str) – Origin of vector. It can be ‘barycenter’ or ‘geocenter’.

Returns

coord – Astropy SkyCoord object with the vector origin -> observer at the given time.

Return type

astropy.coordinates.SkyCoord

sidereal_time(time, mode='local')[source]

Calculates the Apparent Sidereal Time at a reference time.

Parameters

time (str, astropy.time.Time) – Reference time to calculate sidereal time.It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.
mode (str) – Local or greenwich time. If mode set 'local' calculates the sidereal time for the coordinates of this object. If mode set 'greenwich' calculates the Greenwich Apparent Sidereal Time.

Returns

An Astropy Longitude object with the Sidereal Time.

Return type

sidereal_time

to_log(namefile)[source]

Saves the observer log to a file.

Parameters: namefile (str) – Filename to save the log.

The Spacecraft Class

class sora.Spacecraft(name, spkid, ephem='horizons')[source]

Defines a spacecraft observer object.

name

Name for the Observer. Observer is uniquely defined (name must be different for each observer).

Type: str

spkid

spkid of the targeting object.

Type: str, required

ephem

The ephemeris used to locate the observer on space. It can be “horizons” to use horizons or a list of kernels

Type: str, list

get_vector(time, origin='barycenter')[source]

Return the vector Origin -> Observer in the ICRS

Parameters

time (str, astropy.time.Time) – Reference time to calculate the object position. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.
origin (str) – Origin of vector. It can be ‘barycenter’ or ‘geocenter’.

Returns

coord – Astropy SkyCoord object with the vector origin -> observer at the given time.

Return type

astropy.coordinates.SkyCoord

to_log(namefile)[source]

Saves the spacecraft log to a file.

Parameters: namefile (str) – Filename to save the log.

Complementary functions

sora.observer.utils.search_code_mpc()[source]

Reads the MPC Observer Database.

Returns: observatories – A python dictionary with all the sites as Astropy EarthLocation objects.
Return type: dict