Six years after reporting a tentative detection of the methylene radical (CH₂) in 1989, the team of Hollis, Jewell, and Lovas confirmed the detection in 1995. As the authors note, detecting CH₂ is challenging due to a number of factors: only one rotational transition falls within the window where ground-based telscopes can search, and this transition is spread into weaker fine structure lines. Both sets of observations were made with the NRAO 12m telescope. The receiver was upgraded between 1989 and 1995, making better observations possible.