Class IslCrosslinkMeasurement

Nested Relationships

Nested Types

Inheritance Relationships

Base Type

Class Documentation

class IslCrosslinkMeasurement : public lupnt::MeasurementClone<IslCrosslinkMeasurement>

Two-way inter-satellite crosslink range/range-rate (+ optional one-way pseudorange to a known-position transmitter) measurement model for a hub satellite.

The filter state stacks one [r(3), v(3), clock_bias, clock_drift] block per satellite (Config::sub_state_size): block 0 is the hub, blocks 1..n_links are the linked satellites. The model produces, per epoch:

  • 2 * n_links clock-independent two-way crosslink rows [range, range-rate] (RangeAndRangeRate between the hub and each linked block), followed by

  • one one-way pseudorange row per known-position anchor transmitter (e.g. a lunar surface station with a known clock), |r_hub - r_anchor| + C * b_hub.

The Jacobian is taken by autodiff directly on the raw state (not on a reconstructed State), matching the deliberate workaround that keeps the derivative seeds intact for the SchmidtEKF update. This model was previously implemented inline in IslOdtsApp; it now lives here so the application only stages data and wires the model.

Public Functions

IslCrosslinkMeasurement() = default
inline explicit IslCrosslinkMeasurement(Config config)
inline const Config &GetConfig() const
inline void SetConfig(const Config &config)
virtual MeasData Compute(const State &x, MatXd *H = nullptr) const override

Predict the measurement z = h(x), its noise covariance R, and (if H != nullptr) the measurement Jacobian H = dh/dx sized n_z x x.size().

Parameters:

  • x – Estimation state.

  • H – [out] If non-null, filled with the measurement Jacobian; if null, only the value and covariance are computed.

Returns:

MeasData with value = z and covariance = R.

struct Config

Configuration + per-epoch geometry for the combined crosslink/GPS model.

Public Members

int sub_state_size = 8

per-satellite state block size [r,v,cb,cd]

int n_links = 0

number of two-way crosslinks (hub <-> linked sat i)

int idx_position = 0

hub position offset within its state block

int idx_velocity = 3

hub velocity offset

int idx_clock_bias = 6

hub clock-bias offset (for the pseudorange rows)

int idx_clock_drift = 7

hub clock-drift offset (for the anchor Doppler rows)

std::vector<Vec3d> anchor_pos_mci

Known-position anchor transmitter positions [m], hub Moon-centered inertial frame (Frame::MOON_CI), e.g. a lunar surface station; empty for a crosslink-only update.

std::vector<Vec3d> anchor_vel_mci

Anchor inertial velocities [m/s], Frame::MOON_CI (parallel to anchor_pos_mci), required only when include_anchor_doppler is set.

double sigma_range_m = 1.0

two-way crosslink range noise 1-sigma [m]

double sigma_range_rate_mps = 1.0e-3

crosslink range-rate noise 1-sigma [m/s]

double sigma_pseudorange_m = 200.0

one-way anchor pseudorange noise 1-sigma [m]

bool include_anchor_doppler = false

When true, each anchor also yields a one-way Doppler (pseudorange-rate) row, u . (v_hub - v_anchor) + C * clock_drift_hub (u = line of sight), appended after all anchor pseudorange rows. Adds velocity + clock-drift observability.

double sigma_anchor_doppler_mps = 1.0e-3

one-way anchor Doppler noise 1-sigma [m/s]

bool include_time_transfer = false

When true, each two-way crosslink also yields a two-way time-transfer row: the clock-bias difference C * (b_hub - b_link_i) between the two endpoints. Two-way ranging cancels the clocks (its sum-of-one-ways gives range), whereas the difference of the same two one-way exchanges recovers the relative clock offset. These rows are appended after the anchor pseudorange rows.

double sigma_time_transfer_m = 1.0

two-way time-transfer noise 1-sigma [m]

bool include_frequency_transfer = false

When true, each crosslink also yields a two-way frequency-transfer row: the range-rate-equivalent clock-*drift* difference C * (d_hub - d_link_i), appended after the time-transfer rows. This is the rate companion to the time transfer and makes the endpoints’ relative clock drift directly observable.

double sigma_frequency_transfer_mps = 1.0e-3

frequency-transfer noise 1-sigma [m/s]