Click on the button below if you are not able to see the
Astronomy Navigation Menu at your sidebar section.

This page describes the backends available for passive radio astronomy observations. Back-ends for the planetary radar and for the atmospheric science instruments are not described here.

The Wapp Correlators

The WAPP Correlators for pulsar and spectral line observations giving 100-MHz chunks of the full bandwidth of ALFA.

  • Also allows 4 boards of up to 100 MHz each in single-board mode and 8 boards of up to 100 MHz each in dual-board mode for single-pixel observing. (Note: there are 4 WAPP machines: ‘single-board’ and ‘dual-board’ refer to the number of boards employed per machine.)

  • Pulsar capabilities are described here

The Mock Spectrometers

The Mock Spectrometers for spectral line and pulsar observing using the full 300 MHz bandwidth of ALFA and single-pixel observing with 7 × 164 MHz boards or 14 boards with a bandwidth of 82 MHz or less in 7 independently steerable groups.


The Puerto Rico Ultimate Pulsar Processing Instrument, for single-pixel pulsar observations.

GALFA Spectrometers

GALFA Spectrometers – for Galactic HI observations with ALFA

Mark5A & Mark5C

The Mark5A and Mark5C – backends for VLBI observations.

Interim Correlator

The Interim Correlator – an older single-pixel backend providing 4 boards with up-to 50 MHz bandwidth each.

Continuum Observing

Continuum Observing with the Radar Interface – it is normally recommended that for continuum observations one of the spectral-line backends is used. This system is used to provide a continuum total-power record for VLBI observations.