EXPLORER is a cryogenic resonant-mass gravitational wave (GW) detector. It was installed at CERN in 1984 and it has been the first large-mass cryogenic GW antenna to perform long-term continuous operation (since 1990).
EXPLORER is part of the international network of resonant-mass detectors which includes ALLEGRO at the Louisiana State University, Baton Rouge, AURIGA at the INFN Legnaro Laboratories, and NAUTILUS at the INFN Frascati Laboratories.
At the beginning of the year 2000, EXPLORER has been upgraded, with a new small gap capacitive transducer giving high sensitivity on a much larger bandwidth. The minimum detectable spectral amplitude is better than 10^-20 Hz^-1/2 over a frequency band of 50 Hz around 900 Hz. The corresponding sensitivity to short GW bursts is h=2 10^-19. This sensitivity should allow the detection of signal from gravitational collapses and from coalescing and merging neutron stars/black holes binaries in our Galaxy and in Local Group.