NEXRAD May Degrade Mauna Kea Observatory

posted in: October 1993 | 0

One of the few people commenting on the Finding of No Significant Impact for the Moloka’i NEXRAD was Robert McLaren, associate director of the University of Hawai’i’s Institute for Astronomy.

In a letter dated August 13, 1993, McLaren takes exception to the findings contained in the FONSI regarding the impact of NEXRAD’s operations upon telescopes at Mauna Kea and Haleakala. The environmental assessment and FONSI attempted to minimize the impacts by, among other things, noting the presence of other radars in the area that contribute to the ambient “power density” affecting telescope operation. But, McLaren states, the radar that the EA states is to be found at “Pokakula [sic] Training Area” does not exist. Another radar – at the Hilo airport – “operates only between the hours of 6:00 a.m. and 10:00 p.m. Hence,” McLaren continues, “neither of the radars identified in the FONSI contributes to the existing power density on Mauna Kea.”

In correspondence with McLaren, the joint System Program Office had identified still more radars. Again, McLaren found two of these to be non-existent. Instead of the Moloka’i NEXRAD beam being well below the ambient power density at Mauna Kea, McLaren said, in fact it would be two and a half times greater than ambient power.

McLaren takes exception also to the FONSI’s calculation of ambient power levels on Haleakala, where the IFA operates the C.E.K. Mees solar observatory and the Lunar Ranging Experiment (LURE) observatory. McLaren notes that these calculations do not take account of the fact that the telescopes are shielded by terrain from a radar at Kahului airports, so that for Haleakala as well, “The existing power density is almost certainly much lower than that given in the FONSI.”

“To summarize,” his letter states, “the FONSI is seriously inaccurate in its statements about the ambient radar signal levels on Mauna Kea, and the corresponding numbers for Haleakala are almost certainly in error as well… [w]e reiterate our request that either the location or the operating characteristics of the Moloka’i NEXRAD be modified so as to avoid illuminating the observatories on Haleakala and on Mauna Kea with the main beam of the radar.”

As for the Kamuela NEXRAD, McLaren informed JSPO that the predicted power levels it would produce at Mauna Kea are “egregiously high.”

“To date, the NEXRAD program has not proposed any significant mitigation measures…. We are dismayed at the NEXRAD program’s continuing refusal to pursue seriously the only steps which offer any real prospect for mitigation namely relocation of the two NEXRADs and spot blanking,” McLaren concluded. (Spot blanking involves making the radar incapable of sending signals in certain areas of the sky.)

Volume 4, Number 4 October 1993

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