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Interferometry on Mauna Kea

Inside Keck Pictures

Hawai'i - Location, size and extent

The State of Hawai'i is an island group situated in the northern Pacific Ocean, about 2,400 mi (3,900 km) WSW of San Francisco. The smallest of the five Pacific states, Hawaii ranks 47th in size among the 50 states. The 132 Hawaiian Islands have a total area of 6,470 sq mi (16,758 sq km), including 6,425 sq mi (16,641 sq km) of land and only 45 sq mi (117 sq km) of inland water. The island chain extends over 1,576 mi (2,536 km) N-S and 1,425 mi (2,293 km) E-W. The largest island, Hawai'i (known locally as the "Big Island") extends 76 mi (122 km) E-W and 93 mi (150 km) N-S; Oahu, the most populous island, extends 44 mi (71 km) E-W and 30 mi (48 km) N-S.

The eight largest islands of the Hawaiian group are

  • Hawai'i (4,035 sq mi-10, 451 sq km),
  • Maui (734 sq mi-1,901 sq km),
  • O'ahu (617 sq mi-1,598 sq km),
  • Kaua'i (558 sq mi-1,445 sq km),
  • Moloka'i (264 sq mi-684 sq km),
  • Lana'i (141 sq mi-365 sq km),
  • Ni'ihau (73 sq mi-189 sq km),
  • Kaho'olawe (45 sq mi-117 sq km).

The general coastline of the island chain is 750 mi (1,207 km), the tidal shoreline totals 1,052 mi (1,693 km). The state's geographic center is off Maui, at 20°15'n, 156°20'w.

Political map of Hawai'i Satellite View of Hawai'i Hawai'i

Hawai'i - Topography

The 8 major and 124 minor islands that make up the State of Hawai'i were formed by volcanic eruptions. Mauna Loa, on the island of Hawai'i, is the world's largest active volcano, at a height of 13,675 ft (4,168 m). Kilauea, on the eastern slope of Mauna Loa, is the world's largest active volcanic crater: beginning on 24 May 1969, it spewed forth 242 million cu yards (185 million cu m) of lava, spreading over an area of 19.3 sq mi (50 sq km). The longest volcanic eruption in Hawaii lasted 867 days. Further indications of Hawai'i's continuing geological activity are the 14 earthquakes, each with a magnitude of 5 or more on the Richter scale, that shook the islands from 1969 to 1979; one quake, at Puna, on Hawaii in 1975, reached a magnitude of 7.2.

Hawai'i, Maui, Kaua'i, and Moloka'i are the most mountainous islands. The highest peak in the state is Puu Wekiu (13,796 ft/4,208 m), on Hawai'i; the largest natural lake, Halulu (182 acres/74 ha), Ni'ihau; the largest artificial lake, Wai'ia Reservoir (422 acres/171 ha), Kaua'i; and the longest rivers, Kaukonahua Stream (33 mi/53 km) in the north on O'ahu and Wailuku River (32 mi/51 km) on Hawai'i. While much of the Pacific Ocean surrounding the state is up to 20,000 ft (6,100 m) deep, O'ahu, Moloka'i, Lana'i, and Maui stand on a submarine bank at a depth of less than 2,400 ft (730 m).

Hawai'i - Climate

Hawai'i has a tropical climate cooled by trade winds. Normal daily temperatures in Honolulu average 72°F (22°C) in February and 78°F (26°C) in August; the average wind speed is a breezy 11.3 mph (18.2 km/hr). The record high for the state is 100°F (38°C), set at Pahala on 27 April 1931, and the record low is 12°F (11°C), set at Mauna Kea Observatory on 17 May 1979.

Rainfall is extremely variable, with far more precipitation on the windward (northeastern) than on the leeward side of the islands. Mt. Waialeale, Kaua'i, is reputedly the rainiest place on earth, with a mean annual total of 486 in (1,234 cm). Kukui, Maui, holds the US record for the most precipitation in one year739 in (1,878 cm) in 1982. Average annual precipitation in Honolulu (19712000) was 18.3 in (46.5 cm). In the driest areason upper mountain slopes and in island interiors, as in central Mauithe average annual rainfall is less than 10 in (25 cm). Snow falls at the summits of Mauna Loa, Mauna Kea, and Haleakalathe highest mountains. The highest tidal wave (tsunami) in the state's history reached 56 ft (17 m).

Mauna Kea Observatory

The summit of the Mauna Kea is the perfect place to built telescopes for several reasons. First, the summit is at 4200m which is good because the chances to have a clear and nice weather are improved with the altitude. The altitude also reduces the bad effects due to the atmosphere. Then, the fact that Hawai'i is in the middle of the Pacific Ocean implies that the telescopes atop the Mauna Kea will not be polluted by the light of huge agglomerations.

CFHT Hawai'i County Mauna Kea summit Gemini North

These reasons explain why there are so much Observatories atop Mauna Kea. And as you can imagine, those Observatories probe the Universe in the Infrared and visible wavelengths otherwise Mauna Kea situation will not be such excellent.

Keck I and II and Subaru The summit of the Mauna Kea Keck I and II and Subaru

W.M. Keck Observatory

I worked during six months in the Keck Observatory which HQ are in Waimea. The Telescopes are atop the Mauna Kea at 4200m high. I spent most of my time in the HQ to work on the automation, but some times, I went at the summit to work on the interferometer system and it was pretty impressive to see the telescopes and the system itself.

Hawai'i Big Island map with dimensions Headquarters The Keck Observatory

My work

To use Keck I and Keck II in an interferometry configuration, we need to cancel the optical path difference between the two beams. To do this properly, we use the long and the short delay lines. Once they are properly placed, we can do interferometry with the two telescopes.

But, before using the delay lines, we need to align the interferometer so that we are sur that the beams which arrive from space go through the telescopes and through the whole system without any problem. And this is the big and though part.

The Keck defined an alignment procedure divided in 8 steps which are carried out by astronomers before the run so that the interferometer is ready to be used. My work was to allow the astronomers to do the alignment from the HQ, automatically and quickly than man made.

To carry out this project I had to follow several specifications such as the programming language which was Python. I had to develop the classes I needed, to test, valid and integrate the procedures among the Keck system. I also had to write a report so that people from Keck have indications on how to handle my work.

When I left, this project was finished at 80% and astronomers could align the interferometer properly thanks to my work.