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A Python class that allows for convenient conversion between different date and time formats/units

Project description

time_converter build status coverage report

A Python class that allows for convenient conversion between different date and time formats and units. The library supports both general-purpose Earth-based time units (such as Python's datetime type, Day-of-year or POSIX time) as well as time units useful for working with data from the Mars Science Laboratory and Chang'e 4 space missions. It can be easily extended to support additional units.

Note

time_converter was developed in 2019 by Johan von Forstner while he was working on the MSL and LND missions, with the goal of creating a simple API for time unit conversions with little external dependencies.

The conversion between spacecraft clock and UTC is based on a pure Python implementation of the SCLK kernel functionality from NASA's SPICE library, together with the SCLK kernel file that is baked in to the library and needs to be updated occasionally.

As Johan has since left the space science field, this library is no longer under active development - so use it at your own risk.

Especially if very high accuracy (on the order of a few seconds or better) is required and/or the dependency on compiling the SPICE library is not an issue, I would instead recommend to use SPICE directly for MSL SCLK conversions. In Python, this can be done with SpiceyPy or with one of the available wrapper libraries (e.g., ET SPICE).

Installation

pip3 install time_converter

Usage

from time_converter import Time

Time(2019.5, 'decimalyear').to('dt')
# > datetime.datetime(2019, 7, 2, 12, 0)

you can also supply list-like objects as input, the output will be a numpy array.

Time([2018.0, 2018.1], 'decimalyear').to('dt')
# > array([datetime.datetime(2019, 1, 1, 0, 0),
#          datetime.datetime(2019, 2, 6, 11, 59, 59, 999997)], dtype=object)

Supported units

Earth-based time units

Unit Example Name Abbreviated Name
Python datetime (UTC) datetime.datetime(2019, 1, 1, 0, 0) datetime dt
DoY Tuple (year, day of year) (2019, 1.0) doy
Decimal year 2019.0 decimalyear dy
POSIX time 1546300800 posix

Mars Science Laboratory

The MSL spacecraft clock (sclk) measures the number of seconds since January 1 2000, 11:58:55.816 UTC. However, due to drifting of the clock, some corrections need to be applied based on a file supplied by NASA, which this tool uses to do the conversion between sclk and other units.

Unit Example Name
MSL mission sol 2276.8306983767375 sol
MSL spacecraft clock 599570768.5720837 sclk

Chang'E 4

For Chang'E 4, the conversion of spacecraft clock time to datetime has already implemented, so it does not need to be included in time_converter. But we have implemented a converter for the lunar day number and local solar time at Chang'E 4's landing site:

Unit Example Name
Local solar time at Chang'E 4 1, datetime.time(7, 32, 30) ce4lst

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