Class Range

  • All Implemented Interfaces:
    Comparable<ComparableMeasurement>, ComparableMeasurement, ObservedMeasurement<Range>, TimeStamped, ParameterDriversProvider

    public class Range
    extends GroundReceiverMeasurement<Range>
    Class modeling a range measurement from a ground station.

    For one-way measurements, a signal is emitted by the satellite and received by the ground station. The measurement value is the elapsed time between emission and reception multiplied by c where c is the speed of light.

    For two-way measurements, the measurement is considered to be a signal emitted from a ground station, reflected on spacecraft, and received on the same ground station. Its value is the elapsed time between emission and reception multiplied by c/2 where c is the speed of light.

    The motion of both the station and the spacecraft during the signal flight time are taken into account. The date of the measurement corresponds to the reception on ground of the emitted or reflected signal.

    The clock offsets of both the ground station and the satellite are taken into account. These offsets correspond to the values that must be subtracted from station (resp. satellite) reading of time to compute the real physical date. These offsets have two effects:

    • as measurement date is evaluated at reception time, the real physical date of the measurement is the observed date to which the receiving ground station clock offset is subtracted
    • as range is evaluated using the total signal time of flight, for one-way measurements the observed range is the real physical signal time of flight to which (Δtg - Δts) ⨉ c is added, where Δtg (resp. Δts) is the clock offset for the receiving ground station (resp. emitting satellite). A similar effect exists in two-way measurements but it is computed as (Δtg - Δtg) ⨉ c / 2 as the same ground station clock is used for initial emission and final reception and therefore it evaluates to zero.
    Thierry Ceolin, Luc Maisonobe, Maxime Journot