Incorrect transmitter location in BistaticRange measurement

The transmit date is incorrectly calculated by shifting the receive date in the wrong direction. For example

final FieldAbsoluteDate<Gradient> transmitDateDS = downlinkDateDS.shiftedBy(tauTotal);

should be

final FieldAbsoluteDate<Gradient> transmitDateDS = downlinkDateDS.shiftedBy(tauTotal.negate());

This doesn't affect the calculation of the theoretical measurement but does affect the list of participants in the estimated measurement.