The European Space Agency (ESA)-NASA Huygens Recovery Task Force has started a calibration test with the receivers aboard ESA's Huygens Titan lander and NASA Cassini Saturn orbiter in an effort to overcome a communications error on Huygens.
The calibration test will allow new mission scenarios to be developed which can recover the performance of the Huygens-Cassini communications relay link. Huygens is due to transmit data from the vicinity of Saturn's moon Titan to the Cassini mother ship for onward transmission to Earth in November 2004.
During tests in February 2000 it was discovered that the Doppler shift - the change in the apparent frequency and the wavelength of waves due to motion between the two craft - would cause the data signal from Huygens to fall outside the bandwidth of a component in the Cassini receiver (Flight International, 9-15 January). The receiver's bandwidth is too narrow to collect all the data from Huygens which will change its velocity during its 2.5h descent onto Titan. This was apparently overlooked by the Alenia, Alcatel, ESA and NASA design teams.
The current tests will acquire a complete data set that will enable engineers "to fully characterise the radio receivers and thereby enhance an analytical model already worked out", says ESA.
Source: Flight International
