### Install Pyorbital using pip

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Install the Pyorbital package from the Python Package Index (PyPI) using pip.

```bash
pip install pyorbital
```

--------------------------------

### Install Pyorbital using conda

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Install the Pyorbital package from the conda-forge channel using conda.

```bash
conda install -c conda-forge pyorbital
```

--------------------------------

### Install Pyorbital from source (development version)

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Install the latest development version of Pyorbital directly from its GitHub repository using pip.

```bash
pip install git+https://github.com/pytroll/pyorbital.git
```

--------------------------------

### Install Pyorbital from source (editable mode)

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Clone the Pyorbital GitHub repository and install it in editable mode to reflect source code changes immediately.

```bash
git clone git://github.com/pytroll/pyorbital.git
cd pyorbital
pip install -e .
```

--------------------------------

### get_platforms_filepath

Source: https://pyorbital.readthedocs.io/en/latest

Gets the file path for platforms.txt and checks for its existence.

```APIDOC
## pyorbital.tlefile.get_platforms_filepath()

### Description
Get the platforms.txt file path. Check that the file exists or raise an error.

### Usage
This function does not take any arguments.
```

--------------------------------

### Get Satellite Position with Earlier TLE

Source: https://pyorbital.readthedocs.io/en/latest

Demonstrates how using a TLE from a slightly earlier date can result in a different positional calculation.

```python
snpp = Orbital('Suomi NPP', tle_file='/path/to/tle/files/tle-20150131.txt')
snpp.get_lonlatalt(dtobj)
(104.1539184988462, 79.328272480878141, 838.81555967963391)
```

--------------------------------

### Read TLE file and get inclination

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Parse a TLE file using the tlefile module and access satellite parameters like inclination.

```python
from pyorbital import tlefile
tle = tlefile.read('noaa 18', '/path/to/my/tle_file.txt')
tle.inclination
```

--------------------------------

### Get Satellite Position with Specific TLE File

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the satellite's position using a TLE file specified by its path. This is useful for historical data or when internet access is limited.

```python
snpp = Orbital('Suomi NPP', tle_file='/path/to/tle/files/tle-20150207.txt')
snpp.get_lonlatalt(dtobj)
(105.37373804512762, 79.160752404540133, 838.94605490133154)
```

--------------------------------

### Get Satellite Position with Earlier TLE

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Calculates the longitude, latitude, and altitude of the Suomi NPP satellite using a TLE file from January 31, 2015. This demonstrates how TLE date affects orbital calculations.

```python
>>> snpp = Orbital('Suomi NPP', tle_file='/path/to/tle/files/tle-20150131.txt')
>>> snpp.get_lonlatalt(dtobj)
(104.1539184988462, 79.328272480878141, 838.81555967963391)
```

--------------------------------

### Get Satellite Position with Default TLE

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the longitude, latitude, and altitude of a satellite at a specific datetime using its default TLE data.

```python
from pyorbital.orbital import Orbital
import datetime as dt
orb = Orbital("Suomi NPP")
dtobj = dt.datetime(2015,2,7,3,0)
orb.get_lonlatalt(dtobj)
(152.11564698762811, 20.475251739329622, 829.37355785502211)
```

--------------------------------

### Get Satellite Position with Specific TLE

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Calculates the longitude, latitude, and altitude of the Suomi NPP satellite using a TLE file from February 7, 2015. This is useful for historical position tracking.

```python
>>> snpp = Orbital('Suomi NPP', tle_file='/path/to/tle/files/tle-20150207.txt')
>>> snpp.get_lonlatalt(dtobj)
(105.37373804512762, 79.160752404540133, 838.94605490133154)
```

--------------------------------

### main

Source: https://pyorbital.readthedocs.io/en/latest

Runs a test for TLE reading.

```APIDOC
## pyorbital.tlefile.main()

### Description
Run a test TLE reading.

### Usage
This function does not take any arguments.
```

--------------------------------

### TLE Handling

Source: https://pyorbital.readthedocs.io/en/latest

Utilities for downloading, reading, and managing Two-Line Element (TLE) data.

```APIDOC
## Class ChecksumError

### Description
Exception raised for TLE checksum errors.

## Class Downloader

### Description
Handles the downloading and reading of TLE data from various sources.

### Methods
- `fetch_plain_tle()`
- `fetch_spacetrack()`
- `read_tle_files()`
- `read_xml_admin_messages()`

## Variable SATELLITES

### Description
Collection of satellite data.

## Class SQLiteTLE

### Description
Manages TLE data stored in an SQLite database.

### Methods
- `close()`
- `update_db()`
- `write_tle_txt()`

## Class Tle

### Description
Represents a single Two-Line Element set.

### Attributes
- `excentricity` (float)
- `line1` (str)
- `line2` (str)
- `platform` (str)

### Methods
- `to_dict()`

## Function check_is_platform_supported()

### Description
Checks if a given satellite platform is supported.

## Function collect_filenames()

### Description
Collects TLE filenames from a directory.

## Function fetch()

### Description
Fetches TLE data.

## Function get_platforms_filepath()

### Description
Gets the file path for platform TLE data.

## Function main()

### Description
Main entry point for TLE handling operations.

## Function read()

### Description
Reads TLE data from a source.

## Function read_platform_numbers()

### Description
Reads platform numbers from TLE data.

## Function read_tle_from_mmam_xml_file()

### Description
Reads TLE data from a specific MMAM XML file.

## Function read_tles_from_mmam_xml_files()

### Description
Reads TLE data from multiple MMAM XML files.

## Function table_exists()

### Description
Checks if a TLE table exists in the database.
```

--------------------------------

### Configure TLE file path using environment variable

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Set the TLES environment variable to a glob pattern for Pyorbital to find local TLE files.

```bash
TLES=/path/to/tle_files/*/tle*txt
```

--------------------------------

### check_is_platform_supported

Source: https://pyorbital.readthedocs.io/en/latest

Checks if a satellite platform is supported and prints information.

```APIDOC
## pyorbital.tlefile.check_is_platform_supported(_satname_)

### Description
Check if satellite is supported and print info.

### Parameters
- `_satname_`: The name of the satellite platform to check.
```

--------------------------------

### fetch

Source: https://pyorbital.readthedocs.io/en/latest

Fetches TLE data from the internet and saves it to a destination.

```APIDOC
## pyorbital.tlefile.fetch(_destination_)

### Description
Fetch TLE from internet and save it to destination.

### Parameters
- `_destination_`: The path where the TLE data should be saved.
```

--------------------------------

### read

Source: https://pyorbital.readthedocs.io/en/latest

Reads TLE data for a given platform.

```APIDOC
## pyorbital.tlefile.read(_platform_, _tle_file =None_, _line1 =None_, _line2 =None_)

### Description
Read TLE for _platform_. The data are read from _tle_file_ , from _line1_ and _line2_ , from the newest file provided in the TLES pattern, or from internet if none is provided.

### Parameters
- `_platform_`: The satellite platform name.
- `_tle_file` (optional): Path to the TLE file.
- `_line1` (optional): The first line of the TLE.
- `_line2` (optional): The second line of the TLE.
```

--------------------------------

### Check Platform Support

Source: https://pyorbital.readthedocs.io/en/latest

Use the check_platform script to verify if a satellite is supported by Pyorbital and to find its NORAD number. Ensure the PYORBITAL_CONFIG_PATH environment variable is set if using a custom platforms.txt file.

```python
python -m pyorbital.check_platform -s NOAA-21

```

--------------------------------

### Check if a satellite is supported

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Use the check_platform script to verify if a satellite is already supported by Pyorbital and to find its NORAD number.

```python
python -m pyorbital.check_platform -s NOAA-21
```

--------------------------------

### to_dict

Source: https://pyorbital.readthedocs.io/en/latest

Returns the raw, parsed TLE elements as a dictionary.

```APIDOC
## to_dict()

### Description
Return the raw, parsed TLE elements as a dictionary.

### Usage
This method does not take any arguments.
```

--------------------------------

### read_platform_numbers

Source: https://pyorbital.readthedocs.io/en/latest

Reads platform numbers from platforms.txt.

```APIDOC
## pyorbital.tlefile.read_platform_numbers(_filename_, _in_upper =False_, _num_as_int =False_)

### Description
Read platform numbers from $PYORBITAL_CONFIG_PATH/platforms.txt.

### Parameters
- `_filename_`: The name of the file to read.
- `_in_upper` (optional): Whether to read platform names in uppercase. Defaults to False.
- `_num_as_int` (optional): Whether to read numbers as integers. Defaults to False.
```

--------------------------------

### Downloader Class

Source: https://pyorbital.readthedocs.io/en/latest

The Downloader class is used for fetching TLE data from various sources.

```APIDOC
## _class _pyorbital.tlefile.Downloader(_config_)

### Description
Class for downloading TLE data.

### Methods
- **fetch_plain_tle()**: Fetch plain text-formated TLE data.
- **fetch_spacetrack()**: Fetch TLE data from Space-Track.
- **read_tle_files()**: Read TLE data from files.
- **read_xml_admin_messages()**: Read Eumetsat admin messages in XML format.
```

--------------------------------

### read_tles_from_mmam_xml_files

Source: https://pyorbital.readthedocs.io/en/latest

Reads TLE data from a list of MMAM XML files (EUMETSAT).

```APIDOC
## pyorbital.tlefile.read_tles_from_mmam_xml_files(_paths_)

### Description
Read TLE data from a list of MMAM XMl file (EUMETSAT).
MMAM = Multi-Mission Administration Message

### Parameters
- `_paths_`: A list of paths to MMAM XML files.
```

--------------------------------

### get_alt_az

Source: https://pyorbital.readthedocs.io/en/latest

Returns the sun altitude and azimuth for a given UTC time, longitude, and latitude.

```APIDOC
## pyorbital.astronomy.get_alt_az(_utc_time_, _lon_, _lat_)

### Description
Return sun altitude and azimuth from _utc_time_ , _lon_ , and _lat_.

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.
- `lon`: Longitude in degrees.
- `lat`: Latitude in degrees.

### Returns
The returned angles are given in radians.
```

--------------------------------

### SQLiteTLE Class

Source: https://pyorbital.readthedocs.io/en/latest

The SQLiteTLE class provides functionality to store TLE data in a SQLite database.

```APIDOC
## _class _pyorbital.tlefile.SQLiteTLE(_db_location_, _platforms_, _writer_config_)

### Description
Store TLE data in a sqlite3 database.

### Methods
- **close()**: Close the database.
```

--------------------------------

### table_exists

Source: https://pyorbital.readthedocs.io/en/latest

Checks if a table exists in the database.

```APIDOC
## pyorbital.tlefile.table_exists(_db_, _name_)

### Description
Check if the table ‘name’ exists in the database.

### Parameters
- `_db_`: The database object.
- `_name_`: The name of the table to check.
```

--------------------------------

### observer_position

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the observer's ECI position.

```APIDOC
## pyorbital.astronomy.observer_position(_utc_time_, _lon_, _lat_, _alt_)

### Description
Calculate observer ECI position.
http://celestrak.com/columns/v02n03/

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.
- `lon`: Longitude in degrees.
- `lat`: Latitude in degrees.
- `alt`: Altitude in meters.

### Returns
Observer's ECI position.
```

--------------------------------

### sun_ra_dec

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the right ascension and declination of the sun at a given UTC time.

```APIDOC
## pyorbital.astronomy.sun_ra_dec(_utc_time_)

### Description
Right ascension and declination of the sun at _utc_time_.

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.

### Returns
A tuple containing the right ascension and declination of the sun in radians.
```

--------------------------------

### Compute satellite position and velocity

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Calculate the normalized position and velocity of a satellite at a specific time using current TLEs from the internet.

```python
from pyorbital.orbital import Orbital
import datetime as dt
# Use current TLEs from the internet:
orb = Orbital("Suomi NPP")
now = dt.datetime.now(dt.timezone.utc)
# Get normalized position and velocity of the satellite:
orb.get_position(now)
```

--------------------------------

### cos_zen

Source: https://pyorbital.readthedocs.io/en/latest

Derives the cosine of the sun-zenith angle for a given longitude, latitude, and UTC time.

```APIDOC
## pyorbital.astronomy.cos_zen(_utc_time_, _lon_, _lat_)

### Description
Derive the cosine of the sun-zenith angle for _lon_ , _lat_ at _utc_time_.

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.
- `lon`: Longitude in degrees.
- `lat`: Latitude in degrees.

### Returns
Cosine of the sun zenith angle.
```

--------------------------------

### jdays

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the Julian day of a given UTC time.

```APIDOC
## pyorbital.astronomy.jdays(_utc_time_)

### Description
Get the julian day of _utc_time_.

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.

### Returns
The Julian day.
```

--------------------------------

### Read TLE file

Source: https://pyorbital.readthedocs.io/en/latest

Reads a TLE file for a given satellite name. If no path is provided, it attempts to read from local files defined by the TLES environment variable or downloads them from the internet.

```python
>>> from pyorbital import tlefile
>>> tle = tlefile.read('noaa 18', '/path/to/my/tle_file.txt')
>>> tle.inclination
99.043499999999995
```

--------------------------------

### Orbital Computations

Source: https://pyorbital.readthedocs.io/en/latest

Provides classes and methods for calculating orbital elements and satellite positions.

```APIDOC
## Class OrbitElements

### Description
Represents orbital elements and provides methods for related calculations.

### Methods
- `apogee`
- `excentricity`
- `is_circular`
- `is_retrograde`
- `perigee`
- `position_vector_in_orbital_plane()`
- `velocity_at_apogee()`
- `velocity_at_perigee()`

## Class Orbital

### Description
Provides methods for orbital analysis and position determination.

### Methods
- `find_aol()`
- `find_aos()`
- `get_equatorial_crossing_time()`
- `get_last_an_time()`
- `get_lonlatalt()`
- `get_next_passes()`
- `get_observer_look()`
- `get_orbit_number()`
- `get_position()`
- `utc2local()`

## Class OrbitalError

### Description
Custom exception class for orbital computation errors.

## Function get_observer_look()

### Description
Calculates the observer's look angles towards a satellite.

## Function kep2xyz()

### Description
Converts Keplerian elements to Cartesian coordinates.
```

--------------------------------

### Tle Class

Source: https://pyorbital.readthedocs.io/en/latest

Class holding TLE objects.

```APIDOC
## class pyorbital.tlefile.Tle

### Description
Class holding TLE objects.

### Parameters
- `_platform_`: The satellite platform name.
- `_tle_file` (optional): Path to the TLE file.
- `_line1` (optional): The first line of the TLE.
- `_line2` (optional): The second line of the TLE.
```

--------------------------------

### collect_filenames

Source: https://pyorbital.readthedocs.io/en/latest

Collects all filenames from the given paths.

```APIDOC
## pyorbital.tlefile.collect_filenames(_paths_)

### Description
Collect all filenames from _paths_.

### Parameters
- `_paths_`: A list of paths to search for filenames.
```

--------------------------------

### Compute satellite longitude, latitude, and altitude

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Determine the geographic longitude, latitude, and altitude of a satellite at a given time using current TLEs.

```python
from pyorbital.orbital import Orbital
import datetime as dt
# Use current TLEs from the internet:
orb = Orbital("Suomi NPP")
now = dt.datetime.now(dt.timezone.utc)
# Get longitude, latitude and altitude of the satellite:
orb.get_lonlatalt(now)
```

--------------------------------

### read_tle_from_mmam_xml_file

Source: https://pyorbital.readthedocs.io/en/latest

Reads TLE data from a MMAM XML file (EUMETSAT).

```APIDOC
## pyorbital.tlefile.read_tle_from_mmam_xml_file(_fname_)

### Description
Read TLE data from MMAM XMl file (EUMETSAT).
MMAM = Multi-Mission Administration Message

### Parameters
- `_fname_`: The path to the MMAM XML file.
```

--------------------------------

### write_tle_txt

Source: https://pyorbital.readthedocs.io/en/latest

Writes TLE data to a text file.

```APIDOC
## write_tle_txt

### Description
Write TLE data to a text file.

### Usage
This function does not take any arguments.
```

--------------------------------

### Astronomical Computations

Source: https://pyorbital.readthedocs.io/en/latest

Functions for calculating various astronomical parameters and positions.

```APIDOC
## Note on argument types

### Description
Provides guidance on the expected types for function arguments.

## Function cos_zen()

### Description
Calculates the cosine of the zenith angle.

## Function get_alt_az()

### Description
Computes the altitude and azimuth of a celestial object.

## Function gmst()

### Description
Calculates the Greenwich Mean Sidereal Time.

## Function jdays()

### Description
Converts calendar dates to Julian days.

## Function jdays2000()

### Description
Converts calendar dates to Julian days relative to J2000.

## Function observer_position()

### Description
Determines the observer's position.

## Function sun_earth_distance_correction()

### Description
Applies a correction for the Sun-Earth distance.

## Function sun_ecliptic_longitude()

### Description
Calculates the ecliptic longitude of the Sun.

## Function sun_ra_dec()

### Description
Computes the Sun's right ascension and declination.

## Function sun_zenith_angle()

### Description
Calculates the zenith angle of the Sun.
```

--------------------------------

### Orbital Class

Source: https://pyorbital.readthedocs.io/en/latest

The Orbital class is the main interface for orbital computations. It allows users to initialize with satellite data (TLE), and provides methods to find satellite passes, calculate positions, and estimate crossing times.

```APIDOC
## Class Orbital

### Description
Class for orbital computations. The _satellite_ parameter is the name of the satellite to work on and is used to retrieve the right TLE data for internet or from _tle_file_ in case it is provided.

### Methods
- **find_aol(_utc_time_, _lon_, _lat_)**:
  Find Angle of Arrival (AOL).
- **find_aos(_utc_time_, _lon_, _lat_)**:
  Find Angle of السقوط (AOS).
- **get_equatorial_crossing_time(_tstart_, _tend_, _node ='ascending'_, _local_time =False_, _rtol =1e-09_)**:
  Estimate the equatorial crossing time of an orbit. The crossing time is determined via the orbit number, which increases by one if the spacecraft passes the ascending node at the equator. A bisection algorithm is used to find the time of that passage.
  Parameters:
    * **tstart** (datetime): Start time of the orbit.
    * **tend** (datetime): End time of the orbit. Orbit number at the end must be at least one greater than at the start. If there are multiple revolutions in the given time interval, the crossing time of the last revolution in that interval will be computed.
    * **node** (str): Specifies whether to compute the crossing time at the ascending or descending node. Choices: (‘ascending’, ‘descending’).
    * **local_time** (bool): By default the UTC crossing time is returned. Use this flag to convert UTC to local time.
    * **rtol** (float): Tolerance of the bisection algorithm. The smaller the tolerance, the more accurate the result.
- **get_last_an_time(_utc_time_)**:
  Calculate time of last ascending node relative to the specified time.
- **get_lonlatalt(_utc_time_)**:
  Calculate sub-longitude, sub-latitude, and altitude of the satellite.
- **get_next_passes(_utc_time_, _length_, _lon_, _lat_, _alt_, _tol =0.001_, _horizon =0_)**:
  Calculate passes for the next hours for a given start time and a given observer.
  Parameters:
    * **utc_time** (datetime): Observation time.
    * **length** (int): Number of hours to find passes.
    * **lon** (float): Longitude of observer position on ground.
    * **lat** (float): Latitude of observer position on ground.
    * **alt** (float): Altitude above sea-level (geoid) in km of observer position on ground.
    * **tol** (float): Precision of the result in seconds.
    * **horizon** (float): The elevation of the horizon to compute rise time and fall time.
  Returns:
    [(rise-time, fall-time, max-elevation-time), …]
- **get_observer_look(_utc_time_, _lon_, _lat_, _alt_)**:
  Calculate observer's look angle to a satellite.
  Parameters:
    * **utc_time** (datetime): Observation time.
    * **lon** (float): Longitude of observer position on ground in degrees east.
    * **lat** (float): Latitude of observer position on ground in degrees north.
    * **alt** (float): Altitude above sea-level (geoid) of observer position on ground in km.
  Returns:
    (Azimuth, Elevation)
- **get_orbit_number(_utc_time_, _tbus_style =False_, _as_float =False_)**:
  Calculate orbit number at specified time.
  Parameters:
    * **utc_time** (datetime): UTC time as a datetime.datetime object.
    * **tbus_style** (bool): If True, use TBUS-style orbit numbering (TLE orbit number + 1).
    * **as_float** (bool): Return a continuous orbit number as float.
- **get_position(_utc_time_, _normalize =True_)**:
  Get the cartesian position and velocity from the satellite.
- **utc2local(_utc_time_)**:
  Convert UTC to local time.
```

--------------------------------

### Tle Properties

Source: https://pyorbital.readthedocs.io/en/latest

Properties for accessing TLE data.

```APIDOC
## Tle Properties

### `excentricity`

Get ‘eccentricity’ using legacy ‘excentricity’ name.

### `line1`

Return first TLE line.

### `line2`

Return second TLE line.

### `platform`

Return satellite platform name.
```

--------------------------------

### Orbital Error Exception

Source: https://pyorbital.readthedocs.io/en/latest

Custom exception class used within the Orbital module to handle specific orbital computation errors.

```APIDOC
## Exception OrbitalError

### Description
Custom exception for the Orbital class.
```

--------------------------------

### ChecksumError Exception

Source: https://pyorbital.readthedocs.io/en/latest

Custom exception raised when a TLE checksum is invalid.

```APIDOC
## _exception _pyorbital.tlefile.ChecksumError

### Description
ChecksumError.
```

--------------------------------

### gmst

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the Greenwich mean sidereal time in radians.

```APIDOC
## pyorbital.astronomy.gmst(_utc_time_)

### Description
Greenwich mean sidereal utc_time, in radians.
As defined in the AIAA 2006 implementation: http://www.celestrak.com/publications/AIAA/2006-6753/

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.

### Returns
Greenwich mean sidereal time in radians.
```

--------------------------------

### sun_zenith_angle

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the sun-zenith angle for a given longitude, latitude, and UTC time.

```APIDOC
## pyorbital.astronomy.sun_zenith_angle(_utc_time_, _lon_, _lat_)

### Description
Sun-zenith angle for _lon_ , _lat_ at _utc_time_.

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.
- `lon`: Longitude in degrees.
- `lat`: Latitude in degrees.

### Returns
The sun zenith angle returned is in degrees.
```

--------------------------------

### pyorbital.orbital.get_observer_look

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the observer's look angle (azimuth and elevation) towards a satellite at a given time and location.

```APIDOC
## Function get_observer_look

### Description
Calculate observers look angle to a satellite.

### Parameters
- **sat_lon** (float): Satellite longitude.
- **sat_lat** (float): Satellite latitude.
- **sat_alt** (float): Satellite altitude.
- **utc_time** (datetime): Observation time (datetime object).
- **lon** (float): Longitude of observer position on ground in degrees east.
- **lat** (float): Latitude of observer position on ground in degrees north.
- **alt** (float): Altitude above sea-level (geoid) of observer position on ground in km.

### Returns
(Azimuth, Elevation)
```

--------------------------------

### jdays2000

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the number of days since the year 2000.

```APIDOC
## pyorbital.astronomy.jdays2000(_utc_time_)

### Description
Get the days since year 2000.

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.

### Returns
Number of days since year 2000.
```

--------------------------------

### Calculate Sun-Zenith Angle

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Computes the Sun-zenith angle for a given time, longitude, and latitude using the pyorbital.astronomy module. This is useful for remote sensing applications.

```python
>>> from pyorbital import astronomy
>>> import datetime as dt
>>> utc_time = dt.datetime(2012, 5, 15, 15, 45)
>>> lon, lat = 12, 56
>>> astronomy.sun_zenith_angle(utc_time, lon, lat)
62.685986438071602
```

--------------------------------

### update_db

Source: https://pyorbital.readthedocs.io/en/latest

Updates the collected TLE data. Only data with a newer epoch than the existing one is used.

```APIDOC
## update_db

### Description
Updates the collected TLE data. Only data with a newer epoch than the existing one is used.

### Parameters
- `_tle_`: TLE data to update.
- `_source_`: The source of the TLE data.
```

--------------------------------

### OrbitElements Class

Source: https://pyorbital.readthedocs.io/en/latest

The OrbitElements class holds orbital elements and provides properties to compute derived values like apogee, perigee, and eccentricity. It also includes methods to check orbit characteristics such as circularity and retrogradeness.

```APIDOC
## Class OrbitElements

### Description
Class holding the orbital elements.

### Properties
- **apogee** (float): Compute apogee altitude in kilometers.
- **excentricity** (float): Get ‘eccentricity’ using legacy ‘excentricity’ name.
- **is_circular** (bool): Check if orbit is nearly circular.
- **is_retrograde** (bool): Check if orbit is retrograde (inclination > 90°).
- **perigee** (float): Compute perigee altitude in kilometers.

### Methods
- **position_vector_in_orbital_plane()**:
  Compute position vector in the orbital plane at epoch. The x-axis points toward the perigee.
- **velocity_at_apogee()**:
  Compute orbital velocity at apogee in km/s.
- **velocity_at_perigee()**:
  Compute orbital velocity at perigee in km/s.
```

--------------------------------

### Compute satellite position with specific TLE date

Source: https://pyorbital.readthedocs.io/en/latest/_sources/index.rst.txt

Calculate the longitude, latitude, and altitude of a satellite at a specific historical date using its TLE data.

```python
from pyorbital.orbital import Orbital
import datetime as dt
orb = Orbital("Suomi NPP")
dtobj = dt.datetime(2015,2,7,3,0)
orb.get_lonlatalt(dtobj)
```

--------------------------------

### pyorbital.orbital.kep2xyz

Source: https://pyorbital.readthedocs.io/en/latest

Converts Keplerian orbital elements to Cartesian coordinates (x, y, z). Note: The exact meaning of 'kep' is currently unclear and marked for future clarification.

```APIDOC
## Function kep2xyz

### Description
Keplerian to Cartesian coordinates conversion.
(Not sure what ‘kep’ actually refers to, just guessing! FIXME!)

### Parameters
- **kep** (any): Keplerian orbital elements.
```

--------------------------------

### sun_ecliptic_longitude

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the ecliptic longitude of the sun at a given UTC time.

```APIDOC
## pyorbital.astronomy.sun_ecliptic_longitude(_utc_time_)

### Description
Ecliptic longitude of the sun at _utc_time_.

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.

### Returns
The ecliptic longitude of the sun in radians.
```

--------------------------------

### sun_earth_distance_correction

Source: https://pyorbital.readthedocs.io/en/latest

Calculates the sun-earth distance correction, relative to 1 AU.

```APIDOC
## pyorbital.astronomy.sun_earth_distance_correction(_utc_time_)

### Description
Calculate the sun earth distance correction, relative to 1 AU.

### Parameters
- `utc_time`: datetime.datetime instance of the UTC time.

### Returns
The sun-earth distance correction.
```

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