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SPiP : Spacecraft Pixel footprint Projection

Projection of the pixel footprint from an instrument onboard an orbital spacecraft on a planetary surface.

Installation & Update

Method 1: from PyPI (recommended)

Installation: pip3 install planetary-spip

Update: pip3 install planetary-spip --upgrade

Method 2: from the GitHub repository (development version)

Installation: Clone the repository and install with pip:

git clone https://github.com/NAU-PIXEL/spip.git
cd spip
pip3 install .

Update: Go to the previously cloned repository, pull the last updates, and install them with pip:

cd spip
git pull
pip3 install .

Usage

# Package importation
import spip
import numpy as np

# Genaration of a longitude/latitude grid to project the footprint
lon_array = np.arange(0.25, 360, 0.5)   # 0° -> 360°, 2 points per degree
lat_array = np.arange(-89.75, 90, 0.5)  # -90° -> 90°, 2 points per degree
lon_grid, lat_grid = np.meshgrid(lon_array, lat_array)

# Pixel parameters
lon_px, lat_px = 58.2, 79.3         # Longitude/Latitude of the pixel center [deg]
emer = 61.7                         # Emergence angle of the pixel on the surface [deg]
lon_subsc, lat_subsc = 28.0, 24.9   # Longitude/Latitude sub-spacecraft [deg]
d_Mars_sc = 27212                   # Distance aeroid-spacraft [km]
Rmars = spip.emm_emirs.Rmars        # 3390 [km]
ifov = spip.emm_emirs.ifov_emirs    # 2.7e-3 [rad]

# Generation of the mask map of the pixel footprint
#-- EMM/EMIRS spacecraft
mask_footprint = spip.emm_emirs.emirs_ifov_px_projection(
    lon_grid,
    lat_grid,
    lon_px,
    lat_px,
    emer,
    lon_subsc,
    lat_subsc,
    d_Mars_sc,
    Rmars,
    ifov
    )

# To easily handle multiple pixels, there is the spip.emm_emirs.emirs_ifov_multi_px_projection() function.

#-- General case, cirular pixel
a, b, θ = spip.circular_pixels.params_ellipse_fov(
    lon_px,
    lat_px,
    emer,
    lon_subsc,
    lat_subsc,
    d_Mars_sc,
    ifov
    )

mask_footprint = spip.circular_pixels.in_ellipse_spherical(
    lon_grid,
    lat_grid,
    Rmars,
    a,
    b,
    lon_px,
    lat_px,
    θ
    ) * 1.
    
# > mask_footprint
# For each point of the longitude/latitude grid:
#   | 1 -> Within the pixel footprint ellipse.
#   | 0 -> Outside.

Documentation

Planetary Data Workshop 2023: abstract & poster

Credits

© Aurélien Stcherbinine (2023) NAU-PIXEL

Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ, USA

License

This package is released under a MIT open source license. See LICENSE for more details.