Python 2.7下使用Astropy get_gcrs_posvel计算天文台位置速度报错求助

Hey there! Let's work through this issue together. Since you're using Python 2.7 (which is no longer supported) with Astropy's get_gcrs_posvel method, there are a few key areas that are likely causing your error. Here's what to check:

1. Astropy Version Compatibility #

Astropy dropped support for Python 2.7 starting with version 4.0. If you installed a newer version of Astropy in your Python 2.7 environment, that's almost certainly the problem.

• First, check your current Astropy version with this command:

  pip show astropy
  

• If the version is 4.0 or higher, downgrade to the last Python 2.7-compatible release:

  pip install astropy==3.2.3
  

2. Correct Time Object Setup #

In older Astropy versions (compatible with Python 2.7), time objects need to be created with explicit format and scale parameters to avoid parsing errors. For example:

from astropy.time import Time

# Use ISO format with UTC scale (adjust the timestamp to your needs)
obs_time = Time('2024-05-20T12:00:00', format='isot', scale='utc')

Avoid Python 3-specific syntax like f-strings here—stick to .format() for string formatting if you need to dynamically generate timestamps.

3. Valid Observer Location Configuration #

Make sure your Observer object is initialized with properly specified Earth coordinates (including units). Missing units or incorrect coordinate values will throw errors when calling get_gcrs_posvel. Here's a working example:

from astropy.coordinates import EarthLocation, Observer
import astropy.units as u

# Replace with your observatory's actual coordinates
observatory_loc = EarthLocation(
    lon=-118.2858*u.deg,  # Example: Palomar Observatory longitude
    lat=33.3563*u.deg,   # Example: Palomar Observatory latitude
    height=1706*u.m      # Example: Palomar Observatory elevation
)
obs = Observer(location=observatory_loc)

# Get GCRS position and velocity
pos, vel = obs.get_gcrs_posvel(obs_time)

4. Long-Term Note: Migrate to Python 3.x #

While we can fix this for Python 2.7, it's important to remember that Python 2.7 reached end-of-life in 2020. No security updates or bug fixes are released for it, and most modern libraries (including newer Astropy versions) no longer support it. For long-term stability and access to new features, consider migrating your code to Python 3.8 or later.

内容的提问来源于stack exchange，提问作者Miguel Bolón