time_converter 
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. From 2023.10.08, an updated version (mainly updating the LND datetime file to support more lunar days) is available by Zigong Xu. This is package is available again for support LND_loader. All the gitlab link in this package is inactive since the server was shutted down.
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_converterUsage
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 |
Cautions 2023-10-10. Found an not-yet-solve bug when using lunarday equal to 1 as the input of LNDData(1) and Time(1, dt(),'ce4lst'). It appears when we using 1 as the lunar day input, the spiceypy return a empty cell and cause an IndexError. This issue should relat to the version of spiceypy since the original time_converter worked. The current version is spiceypy==6.0.0. I propose that when using the lunarday as the input time or when constructing ce4lst Time variable, add extra 1 to the input, like following:
Lunarday = 1
Data = LNDData(Lunarday + 1)
**Or**
Time((Lunarday + 1, dt()),'ce4lst')By doing so, I avoid changing the Time_converter package but fix the error when using time_converter. A weird usage need to keep in mind.