The project belonged to a larger scientific obsession of the early twentieth century. Abbot, who directed the Smithsonian Astrophysical Observatory from 1906 to 1944, believed that small variations in the solar constant -- the total energy the sun delivers to Earth -- could explain weather patterns. He had already established observatories in Chile and Arizona to measure solar irradiance, but the small variations they detected needed independent confirmation from a third site. In March 1925, the National Geographic Society granted funds to find and equip that site. After considering locations near the town of Aus and at the Spitzkoppe, Abbot traveled to Brukkaros Mountain, roughly 100 kilometers north of Keetmanshoop, and selected a spot on the southwestern rim of the crater, just below the lip. The mountain's isolation promised clear skies. Its elevation of about 1,510 meters seemed adequate. Both assumptions would prove only partially correct.

Construction began with blasting. Workers excavated a shallow tunnel three meters wide and just over two meters high into the rock, then extended it outward with cemented stone walls and a concrete roof to a total length of 10.5 meters. Wooden partitions divided the interior into three small rooms. Outside, a stone platform held the primary instruments: an Abbot silver-disk pyrheliometer on an equatorial mount, which tracked the sun by turning a single screw, and a pyranometer that measured the sky's diffuse radiation while excluding the sun itself. A pendulum beating half-seconds kept time, while a theodolite measured the sun's altitude so that atmospheric absorption could be calculated. Inside the tunnel, a coelostat -- two flat mirrors of stellite, a tarnish-resistant cobalt alloy, one driven by clockwork -- reflected sunlight through an opening in the northern wall onto a bolometer that recorded the sun's spectrum across visible and infrared wavelengths. The design replicated the existing observatories in Chile and Arizona. Regular weather observations began on 11 August 1927 and were reported to the Weather Bureau in Windhoek.

For three years, Hoover and Greeley kept the instruments running, a two-person team performing measurements that required extraordinary precision in a place that offered very little else. In September 1929, Louis O. Sordahl and his assistant A.G. Froiland replaced them. Sordahl brought his wife Margaret, a naturalist who used the posting to collect mammal, bird, reptile, insect, and plant specimens from the surrounding desert, later donating them to the National Museum of Natural History in Washington. When Froiland was recalled in March 1931, his replacement -- a South African named Arthur Bleksley -- stayed only six months before accepting a permanent position in Johannesburg. The next assistant, D.J. Hatting, lasted four weeks. Margaret Sordahl began taking over the scientific work herself. The observatory was becoming difficult to staff, and its results were becoming difficult to trust.

The problem was the atmosphere. Brukkaros sat at a relatively low elevation compared to the observatories in Chile and Arizona, which meant that the column of air between the instruments and the sun was thicker and more variable. Compensating for atmospheric absorption -- the entire mathematical basis of the solar constant calculation -- proved unreliable under these conditions. The values fluctuated in ways that could not be cleanly separated from genuine solar variation. When Abbot later recomputed daily solar constant values for the period 1923 to 1939, he distanced himself sharply from Brukkaros, describing its results as "so far inferior that its results have not been reduced" and "subject to sources of error which we have now eliminated." The instruments were returned to Washington and donated to the Smithsonian by the National Geographic Society. They were later redeployed to observatories in Egypt. Abbot's broader claim -- that the solar constant varied measurably and that these variations drove weather -- never convinced most meteorologists, regardless of which observatory produced the data.

The observatory closed after just five years, a failure by its own stated goals. But the 3,000 pyrheliometer measurements of solar irradiance collected at Brukkaros turned out to have a second life. When the South African Weather Bureau launched a country-wide radiation survey in 1952, the Brukkaros data represented the longest continuous series of solar radiation measurements from the central plateau of southern Africa. Scientists used the data for two purposes: calculating how much solar energy was available at different times of day and year for potential industrial applications, and estimating total radiation -- sun plus sky -- for climatological studies. The ruins of the observatory still sit inside the crater of Brukkaros Mountain, stone walls and concrete slowly yielding to the Namibian elements. The mountain itself, a volcanic remnant rising from the flat scrubland of the Karas Region, remains one of the more striking geological features visible from the air in southern Namibia.