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@jklenzing
jklenzing committed Oct 29, 2021
2 parents a6121b4 + e30e101 commit 82f4e4c
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3 changes: 2 additions & 1 deletion CHANGELOG.md
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Expand Up @@ -2,9 +2,10 @@
All notable changes to this project will be documented in this file.
This project adheres to [Semantic Versioning](https://semver.org/).

## [0.3.0] - 2021-06-24
## [0.3.0] - 2021-08-05
* Add Keplerian orbital inputs into missions_sgp4
* Update sgp4 interface to use new syntax for initialization from TLEs
* Include conversions to geodetic latitude / longitude / altitude for sgp4
* Improve metadata generation in missions_sgp4
* Documentation
* Improve docstrings throughout
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62 changes: 31 additions & 31 deletions pysatMissions/instruments/missions_ephem.py
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Expand Up @@ -211,38 +211,38 @@ def load(fnames, tag=None, inst_id=None, obs_long=0., obs_lat=0., obs_alt=0.,
index=index)
data.index.name = 'Epoch'

return data, meta.copy()
meta = pysat.Meta()
meta['Epoch'] = {
meta.labels.units: 'Milliseconds since 1970-1-1',
meta.labels.notes: 'UTC time at middle of geophysical measurement.',
meta.labels.desc: 'UTC seconds',
meta.labels.name: 'Time index in milliseconds'}
meta['glong'] = {meta.labels.units: 'degrees',
meta.labels.desc: 'WGS84 geodetic longitude'}
meta['glat'] = {meta.labels.units: 'degrees',
meta.labels.desc: 'WGS84 geodetic latitude'}
meta['alt'] = {meta.labels.units: 'km',
meta.labels.desc: "WGS84 height above Earth's surface"}
for v in ['x', 'y', 'z']:
meta['position_ecef_{:}'.format(v)] = {
meta.labels.units: 'km',
meta.labels.name: 'ECEF {:}-position'.format(v),
meta.labels.desc: 'Earth Centered Earth Fixed {:}-position'.format(v)}
meta['obs_sat_az_angle'] = {
meta.labels.units: 'degrees',
meta.labels.name: 'Satellite Azimuth Angle',
meta.labels.desc: 'Azimuth of satellite from ground station'}
meta['obs_sat_el_angle'] = {
meta.labels.units: 'degrees',
meta.labels.name: 'Satellite Elevation Angle',
meta.labels.desc: 'Elevation of satellite from ground station'}
meta['obs_sat_slant_range'] = {
meta.labels.units: 'km',
meta.labels.name: 'Satellite Slant Distance',
meta.labels.desc: 'Distance of satellite from ground station'}

return data, meta


list_files = functools.partial(ps_meth.list_files, test_dates=_test_dates)
download = functools.partial(ps_meth.download)

# Create metadata corresponding to variables in load routine just above.
# Defined here here rather than above to avoid regeneration at every load call.
meta = pysat.Meta()
meta['Epoch'] = {
meta.labels.units: 'Milliseconds since 1970-1-1',
meta.labels.notes: 'UTC time at middle of geophysical measurement.',
meta.labels.desc: 'UTC seconds',
meta.labels.name: 'Time index in milliseconds'}
meta['glong'] = {meta.labels.units: 'degrees',
meta.labels.desc: 'WGS84 geodetic longitude'}
meta['glat'] = {meta.labels.units: 'degrees',
meta.labels.desc: 'WGS84 geodetic latitude'}
meta['alt'] = {meta.labels.units: 'km',
meta.labels.desc: "WGS84 height above Earth's surface"}
meta['position_ecef_x'] = {meta.labels.units: 'km',
meta.labels.desc: 'ECEF x co-ordinate of satellite'}
meta['position_ecef_y'] = {meta.labels.units: 'km',
meta.labels.desc: 'ECEF y co-ordinate of satellite'}
meta['position_ecef_z'] = {meta.labels.units: 'km',
meta.labels.desc: 'ECEF z co-ordinate of satellite'}
meta['obs_sat_az_angle'] = {
meta.labels.units: 'degrees',
meta.labels.desc: 'Azimuth of satellite from ground station'}
meta['obs_sat_el_angle'] = {
meta.labels.units: 'degrees',
meta.labels.desc: 'Elevation of satellite from ground station'}
meta['obs_sat_slant_range'] = {
meta.labels.units: 'km',
meta.labels.desc: 'Distance of satellite from ground station'}
161 changes: 118 additions & 43 deletions pysatMissions/instruments/missions_sgp4.py
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Expand Up @@ -23,6 +23,9 @@
from pysat.instruments.methods import testing as ps_meth
from pysatMissions.instruments import _core as mcore
from pysatMissions.instruments.methods import orbits

from geospacepy import terrestrial_ellipsoidal as conv_ell
from geospacepy import terrestrial_spherical as conv_sph
from sgp4 import api as sapi

logger = pysat.logger
Expand Down Expand Up @@ -65,10 +68,10 @@ def init(self):
clean = mcore._clean


def load(fnames, tag=None, inst_id=None,
TLE1=None, TLE2=None, alt_periapsis=None, alt_apoapsis=None,
inclination=None, raan=None, arg_periapsis=None, mean_anomaly=None,
bstar=None, num_samples=None, cadence='1S'):
def load(fnames, tag=None, inst_id=None, TLE1=None, TLE2=None,
alt_periapsis=None, alt_apoapsis=None,
inclination=None, raan=0., arg_periapsis=0., mean_anomaly=0.,
bstar=0., one_orbit=False, num_samples=None, cadence='1S'):
"""Generate position of satellite in ECI co-ordinates.
Note
Expand All @@ -86,39 +89,51 @@ def load(fnames, tag=None, inst_id=None,
specifies the number of seconds to simulate the satellite)
(default='')
TLE1 : string
First string for Two Line Element. Must be in TLE format
First string for Two Line Element. Must be in TLE format. TLE1 and TLE2
both required if instantiating instrument by TLEs. (defalt=None)
TLE2 : string
Second string for Two Line Element. Must be in TLE format
Second string for Two Line Element. Must be in TLE format. TLE1 and TLE2
both required if instantiating instrument by TLEs. (defalt=None)
alt_periapsis : float
The lowest altitude from the mean planet surface along the orbit (km)
The lowest altitude from the mean planet surface along the orbit (km).
Required along with inclination if instantiating via orbital elements.
(defalt=None)
alt_apoapsis : float or NoneType
The highest altitude from the mean planet surface along the orbit (km)
If None, assumed to be equal to periapsis. (default=None)
If None, assumed to be equal to periapsis (ie, circular orbit). Optional
when instantiating via orbital elements. (default=None)
inclination : float
Orbital Inclination in degrees (default=None)
Orbital Inclination in degrees. Required along with alt_periapsis if
instantiating via orbital elements. (default=None)
raan : float
Right Ascension of the Ascending Node (RAAN) in degrees. This defines
the orientation of the orbital plane to the generalized reference frame.
The Ascending Node is the point in the orbit where the spacecraft passes
through the plane of reference moving northward. For Earth orbits, the
location of the RAAN is defined as the angle eastward of the First Point
of Aries.
(default=None)
of Aries. Optional when instantiating via orbital elements.
(default=0.)
arg_periapsis : float
Argument of Periapsis in degrees. This defines the orientation of the
ellipse in the orbital plane, as an angle measured from the ascending
node to the periapsis (default=None)
node to the periapsis. Optional when instantiating via orbital elements.
(default=0.)
mean_anomaly : float
The fraction of an elliptical orbit's period that has elapsed since the
orbiting body passed periapsis. Note that this is a "fictitious angle"
(input in degrees) which defines the location of the spacecraft in the
orbital plane based on the orbital period.
(default=None)
orbital plane based on the orbital period. Optional when instantiating
via orbital elements.
(default=0.)
bstar : float
Inverse of the ballistic coefficient. Used to model satellite drag.
Measured in inverse distance (1 / earth radius). (default=None)
Measured in inverse distance (1 / earth radius). Optional when
instantiating via orbital elements. (default=0.)
one_orbit : bool
Flag to override num_samples and only provide a single orbit.
(default=False)
num_samples : int
Number of samples per day
Number of samples per day. (default=None)
cadence : str
Uses pandas.frequency string formatting ('1S', etc)
(default='1S')
Expand Down Expand Up @@ -154,8 +169,8 @@ def load(fnames, tag=None, inst_id=None,
if TLE2 is not None:
line2 = TLE2

if num_samples is None:
num_samples = 100
if (num_samples is None) or one_orbit:
num_samples = 86400

# Extract list of times from filenames and inst_id
times, index, dates = ps_meth.generate_times(fnames, num_samples,
Expand All @@ -177,6 +192,12 @@ def load(fnames, tag=None, inst_id=None,
else:
# Otherwise, use TLEs
satellite = sapi.Satrec.twoline2rv(line1, line2, sapi.WGS72)
mean_motion = satellite.mm

if one_orbit:
ind = times <= (2 * np.pi / mean_motion * 60)
times = times[ind]
index = index[ind]

jd = jd * np.ones(len(times))
fr = times / 86400.
Expand All @@ -188,13 +209,36 @@ def load(fnames, tag=None, inst_id=None,
if np.any(err_code == i):
raise ValueError(sapi.SGP4_ERRORS[i])

# Add ECEF values to instrument.

pos_ecef = conv_sph.eci2ecef(position, (jd + fr))
vel_ecef = conv_sph.eci2ecef(velocity, (jd + fr))

# Convert to geocentric latitude, longitude, altitude.
lat, lon, rad = conv_sph.ecef_cart2spherical(pos_ecef)
# Convert to geodetic latitude, longitude, altitude.
# Ellipsoidal conversions require input in meters.
geod_lat, geod_lon, geod_alt = conv_ell.ecef_cart2geodetic(pos_ecef * 1000.)

# Put data into DataFrame
data = pds.DataFrame({'position_eci_x': position[:, 0],
'position_eci_y': position[:, 1],
'position_eci_z': position[:, 2],
'velocity_eci_x': velocity[:, 0],
'velocity_eci_y': velocity[:, 1],
'velocity_eci_z': velocity[:, 2]},
'velocity_eci_z': velocity[:, 2],
'position_ecef_x': pos_ecef[:, 0],
'position_ecef_y': pos_ecef[:, 1],
'position_ecef_z': pos_ecef[:, 2],
'velocity_ecef_x': vel_ecef[:, 0],
'velocity_ecef_y': vel_ecef[:, 1],
'velocity_ecef_z': vel_ecef[:, 2],
'latitude': lat,
'longitude': lon,
'mean_altitude': rad - 6371.2,
'geod_latitude': geod_lat,
'geod_longitude': geod_lon,
'geod_altitude': geod_alt / 1000.}, # Convert to km
index=index)
data.index.name = 'Epoch'

Expand All @@ -205,32 +249,63 @@ def load(fnames, tag=None, inst_id=None,
meta.labels.notes: 'UTC time at middle of geophysical measurement.',
meta.labels.desc: 'UTC seconds',
meta.labels.name: 'Time index in milliseconds'}
meta['position_eci_x'] = {
meta.labels.units: 'km',
meta.labels.name: 'ECI x-position',
meta.labels.desc: 'Earth Centered Inertial x-position of satellite.'}
meta['position_eci_y'] = {
for v in ['x', 'y', 'z']:
meta['position_eci_{:}'.format(v)] = {
meta.labels.units: 'km',
meta.labels.name: 'ECI {:}-position'.format(v),
meta.labels.desc: 'Earth Centered Inertial {:}-position'.format(v)}
meta['velocity_eci_{:}'.format(v)] = {
meta.labels.units: 'km/s',
meta.labels.name: 'Satellite velocity ECI-{:}'.format(v),
meta.labels.desc: 'Satellite velocity along ECI-{:}'.format(v)}
meta['position_ecef_{:}'.format(v)] = {
meta.labels.units: 'km',
meta.labels.notes: 'Calculated using geospacepy.terrestrial_spherical',
meta.labels.name: 'ECEF {:}-position'.format(v),
meta.labels.desc: 'Earth Centered Earth Fixed {:}-position'.format(v)}
meta['velocity_ecef_{:}'.format(v)] = {
meta.labels.units: 'km',
meta.labels.notes: 'Calculated using geospacepy.terrestrial_spherical',
meta.labels.name: 'ECEF {:}-velocity'.format(v),
meta.labels.desc: 'Earth Centered Earth Fixed {:}-velocity'.format(v)}
meta['latitude'] = {
meta.labels.units: 'degrees',
meta.labels.notes: 'Calculated using geospacepy.terrestrial_spherical',
meta.labels.name: 'Geocentric Latitude',
meta.labels.desc: 'Geocentric Latitude of satellite',
meta.labels.min_val: -90.,
meta.labels.max_val: 90.}
meta['longitude'] = {
meta.labels.units: 'degrees',
meta.labels.notes: 'Calculated using geospacepy.terrestrial_spherical',
meta.labels.name: 'Geocentric Longitude',
meta.labels.desc: 'Geocentric Longitude of satellite',
meta.labels.min_val: -180.,
meta.labels.max_val: 180.}
meta['mean_altitude'] = {
meta.labels.units: 'km',
meta.labels.name: 'ECI y-position',
meta.labels.desc: 'Earth Centered Inertial y-position of satellite.'}
meta['position_eci_z'] = {
meta.labels.notes: 'Calculated using geospacepy.terrestrial_spherical',
meta.labels.name: 'Altitude',
meta.labels.desc: 'Altitude of satellite above an ellipsoidal Earth'}
meta['geod_latitude'] = {
meta.labels.units: 'degrees',
meta.labels.notes: 'Calculated using geospacepy.terrestrial_ellipsoidal',
meta.labels.name: 'Geodetic Latitude',
meta.labels.desc: 'Geodetic Latitude of satellite',
meta.labels.min_val: -90.,
meta.labels.max_val: 90.}
meta['geod_longitude'] = {
meta.labels.units: 'degrees',
meta.labels.notes: 'Calculated using geospacepy.terrestrial_ellipsoidal',
meta.labels.name: 'Geodetic Longitude',
meta.labels.desc: 'Geodetic Longitude of satellite',
meta.labels.min_val: -180.,
meta.labels.max_val: 180.}
meta['geod_altitude'] = {
meta.labels.units: 'km',
meta.labels.name: 'ECI z-position',
meta.labels.desc: 'Earth Centered Inertial z-position of satellite.'}
meta['velocity_eci_x'] = {
meta.labels.units: 'km/s',
meta.labels.desc: 'Satellite velocity along ECI-x',
meta.labels.name: 'Satellite velocity ECI-x'}
meta['velocity_eci_y'] = {
meta.labels.units: 'km/s',
meta.labels.desc: 'Satellite velocity along ECI-y',
meta.labels.name: 'Satellite velocity ECI-y'}
meta['velocity_eci_z'] = {
meta.labels.units: 'km/s',
meta.labels.desc: 'Satellite velocity along ECI-z',
meta.labels.name: 'Satellite velocity ECI-z'}

# TODO(#56): add call for GEI/ECEF translation here
meta.labels.notes: 'Calculated using geospacepy.terrestrial_ellipsoidal',
meta.labels.name: 'Altitude',
meta.labels.desc: 'Altitude of satellite above an ellipsoidal Earth'}

return data, meta

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65 changes: 15 additions & 50 deletions pysatMissions/methods/spacecraft.py
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Expand Up @@ -79,44 +79,15 @@ def add_ram_pointing_sc_attitude_vectors(inst):
inst['sc_yhat_ecef_z'])

# Adding metadata
inst.meta['sc_xhat_ecef_x'] = {
'units': '',
'desc': ' '.join(('S/C attitude (x-direction, ram) unit vector,',
'expressed in ECEF basis, x-component'))}
inst.meta['sc_xhat_ecef_y'] = {
'units': '',
'desc': ' '.join(('S/C attitude (x-direction, ram) unit vector,',
'expressed in ECEF basis, y-component'))}
inst.meta['sc_xhat_ecef_z'] = {
'units': '',
'desc': ' '.join(('S/C attitude (x-direction, ram) unit vector,',
'expressed in ECEF basis, z-component'))}

inst.meta['sc_zhat_ecef_x'] = {
'units': '',
'desc': ' '.join(('S/C attitude (z-direction, generally nadir) unit',
'vector, expressed in ECEF basis, x-component'))}
inst.meta['sc_zhat_ecef_y'] = {
'units': '',
'desc': ' '.join(('S/C attitude (z-direction, generally nadir) unit',
'vector, expressed in ECEF basis, y-component'))}
inst.meta['sc_zhat_ecef_z'] = {
'units': '',
'desc': ' '.join(('S/C attitude (z-direction, generally nadir) unit',
'vector, expressed in ECEF basis, z-component'))}

inst.meta['sc_yhat_ecef_x'] = {
'units': '',
'desc': ' '.join(('S/C attitude (y-direction, generally south) unit',
'vector, expressed in ECEF basis, x-component'))}
inst.meta['sc_yhat_ecef_y'] = {
'units': '',
'desc': ' '.join(('S/C attitude (y-direction, generally south) unit',
'vector, expressed in ECEF basis, y-component'))}
inst.meta['sc_yhat_ecef_z'] = {
'units': '',
'desc': ' '.join(('S/C attitude (y-direction, generally south) unit',
'vector, expressed in ECEF basis, z-component'))}
for v in ['x', 'y', 'z']:
for u in ['x', 'y', 'z']:
inst.meta['sc_{:}hat_ecef_{:}'.format(v, u)] = {
inst.meta.labels.units: '',
inst.meta.labels.name: 'SC {:}-unit vector, ECEF-{:}'.format(v, u),
inst.meta.labels.desc: ' '.join(('S/C attitude ({:}'.format(v),
'-direction, ram) unit vector,',
'expressed in ECEF basis,',
'{:}-component'.format(u)))}

# check what magnitudes we get
mag = np.sqrt(inst['sc_zhat_ecef_x']**2 + inst['sc_zhat_ecef_y']**2
Expand Down Expand Up @@ -164,18 +135,12 @@ def get_vel_from_pos(x):
inst[1:-1, 'velocity_ecef_y'] = vel_y
inst[1:-1, 'velocity_ecef_z'] = vel_z

inst.meta['velocity_ecef_x'] = {'units': 'km/s',
'desc': ' '.join(('Velocity of satellite',
'calculated with respect',
'to ECEF frame.'))}
inst.meta['velocity_ecef_y'] = {'units': 'km/s',
'desc': ' '.join(('Velocity of satellite',
'calculated with respect',
'to ECEF frame.'))}
inst.meta['velocity_ecef_z'] = {'units': 'km/s',
'desc': ' '.join(('Velocity of satellite',
'calculated with respect',
'to ECEF frame.'))}
for v in ['x', 'y', 'z']:
inst.meta['velocity_ecef_{:}'.format(v)] = {
inst.meta.labels.units: 'km/s',
inst.meta.labels.name: 'ECEF {:}-velocity'.format(v),
inst.meta.labels.desc: ' '.join(('Velocity of satellite calculated',
'with respect to ECEF frame.'))}
return


Expand Down

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