Manual Observation Collections

In addition to loading pre-defined file types (such as ODF or IFMS files), or simulating observations within the Tudat environment, users can manually create an ObservationCollection from external data sources, such as experimental measurements or pre-processed Python arrays. This allows the use of Tudat’s estimation and plotting utilities on user-provided datasets.

Defining Single Observation Sets

The building block of a manual collection is the SingleObservationSet. This object encapsulates the data for a specific observable type associated with a specific link definition.

To create a single observation set, you must define the link ends, provide the observation times and values, and specify the reference link end.

from tudatpy.estimation import observations
from tudatpy.estimation import observable_models_setup
import numpy as np

# 1. Define the link ends
link_ends = {
    observable_models_setup.links.transmitter:
        observable_models_setup.links.body_origin_link_end_id("Starship"),
    observable_models_setup.links.receiver:
        observable_models_setup.links.body_reference_point_link_end_id("Earth", "Goldstone")
}

# 2. Prepare the data (times in seconds since J2000, observations in SI units)
times = np.array([1.0e7, 1.0e7 + 300, 1.0e7 + 600])

# Angular observations (RA/Dec) must be provided in radians
obs_values = np.array([
    [np.deg2rad(120.0), np.deg2rad(10.0)],
    [np.deg2rad(120.2), np.deg2rad(10.1)],
    [np.deg2rad(120.4), np.deg2rad(10.2)]
])

# 3. Create the set
angular_set = observations.create_single_observation_set(
    observable_models_setup.model_settings.angular_position_type,
    link_ends,
    obs_values,
    times,
    observable_models_setup.links.receiver
)

Note

When creating a manual observation collection, it is recommended to adhere to Tudatpy’s default SI units: meters for distance, radians for angles, and seconds for time.