The following information obtained from UNAVCO's online DOI system:
(https://www.unavco.org/data/doi/search/search.html)

SCIGN USGS GPS Network - TOWG-Tower 2 GPS P.S.
Start: 12-Aug-2015
End: 04-Dec-2019
Hudnut, Kenneth, Determan, Daniel N., Aspiotes, Aris G., 2015, SCIGN USGS GPS Network - TOWG-Tower 2 GPS P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5DZ06N6