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

PBO GPS Network - AB04-Savoonga__AK2007 P.S.
Start: 06-Jul-2007
End: 07-Oct-2020
UNAVCO Community, 2007, PBO GPS Network - AB04-Savoonga__AK2007 P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5X06510