FIRST SPECTRA FROM A NEW, WIDE-BAND, HYBRID DIGITAL CORRELATOR SPECTROMETER FOR THE FIRST-HIFI INSTRUMENT

We have designed and built a new, wide band, modulable resolution spec trometer, in view of full astronomical qualifying tests, and to prepar e future models for the FIRST satellite's heterodyne instrument. Our s pectrometer, a hybrid digital Autocorrelator, offers flexibility in te rms of bandwidth (from 170MHz to 680MHz) and resolution (from 700kHz t o 3MHz). This spectrometer required the development of a dedicated ana log filter bank, homemade samplers, and the design of full custom GaAs integrated circuits. Laboratory tests have shown excellent agreement with expected performances and observations performed with the IRAM 30 -m radiotelescope have qualified its capabilities. Despite the relativ ely limited number of channels of our current prototype compared to ot hers spectrometers, the main advantages are its stability (inherent to digital technique), and its spectral versatility. Recent microelectro nics advances and rad-tolerance of our spectrometer components are use d to prepare a new, compact, and low power consumption autocorrelator in view of a flight model for HIFI, the heterodyne instrument on the E SA cornerstone mission FIRST.