Context : The THz atmospheric “ windows , ” centered at roughly 1.3 and 1.5 THz , contain numerous spectral lines of astronomical importance , including three high-J CO lines , the [ N II ] line at 205 \mu m , and the ground transition of para-H _ { 2 } D ^ { + } .
The CO lines are tracers of hot ( several 100 K ) , dense gas ; [ N II ] is a cooling line of diffuse , ionized gas ; the H _ { 2 } D ^ { + } line is a non-depleting tracer of cold ( \sim 20 K ) , dense gas .

Aims : As the THz lines benefit the study of diverse phenomena ( from high-mass star-forming regions to the WIM to cold prestellar cores ) , we have built the CO N ^ { + } D euterium O bservations R eceiver ( CONDOR ) to further explore the THz windows by ground-based observations .

Methods : CONDOR was designed to be used at the Atacama Pathfinder EXperiment ( APEX ) and Stratospheric Observatory For Infrared Astronomy ( SOFIA ) .
CONDOR was installed at the APEX telescope and test observations were made to characterize the instrument .

Results : The combination of CONDOR on APEX successfully detected THz radiation from astronomical sources .
CONDOR operated with typical T _ { rec } = 1600 K and spectral Allan variance times of \sim 30 s. CONDOR ’ s “ first light ” observations of CO 13-12 emission from the hot core Orion FIR4 ( = OMC1 South ) revealed a narrow line with T _ { MB } \approx 210 K and \Delta V \approx 5.4 km s ^ { -1 } .
A search for [ N II ] emission from the ionization front of the Orion Bar resulted in a non-detection .

Conclusions : The successful deployment of CONDOR at APEX demonstrates the potential for making observations at THz frequencies from ground-based facilities .