The spectrum is measured over {HEAD ~ a time period} of {TAIL ~ 1 to 1000 seconds}, at intervals of 5 to 10 milliseconds or less 
The spectrum is measured over { HEAD ~ a time period } of { TAIL ~ 1 to 1000 seconds } , at intervals of 5 to 10 milliseconds or less
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH