Walt Roberts' assignment at the Climax Observatory was to last only one year, but, with the country's sudden entry into the war, he remained at Climax as sole observer, making daily observations of the solar chromosphere and corona.

Some filaments and prominences can reach impressive sizes, and remain visible very far above the solar disk. This prominence was photographed in June 1946 again through a filter centered on H-alpha, and extends some 200000 km above the solar surface; the Earth would easily fit under it. The bright arch at the bottom of the picture delineates the solar limb. Prominences extending so far up above the photosphere are usually not static, but are expanding outward in an eruptive phase.

HAO's laboratories were relocated to the CU campus in 1948. HAO's laboratories were relocated to the CU campus. In the mid-50's HAO and CU cooperated to establish the Summers-Bausch Observatory (seen on left side of photo). During the last half of the 1950s, HAO scientists pooled their talents with CU's faculty to form the University's Department of Astro-Geophysics. The Astro-Geophysics building (seen on right side of the photo) was dedicated October 8, 1960.

Jack Evans makes preliminary measurements on two large quartz crystals in order to construct a quartz monochromator. Quartz slabs cut from these crystals were layered and spaced to create a "birefringent filter". Bernard Lyot had pointed out how such a filter could operate, but it was Evans who perfected the construction process. The birefringent filters are capable of transmitting very narrow wavelength (~5 angstroms at a time in any part of the spectrum) bands of electromagnetic radiation.

The delicate job of grinding a 16 inch lens for an "inside-out" telescope or coronagraph is under way in the Boulder optical shop of HAO. Pictured adjusting the grinding mechanism are Frederick B. Pearson (left) chief optician for the observatory, and Dr. John W. Evans, noted optical physicist and member of the observatory staff. Two 26 foot coronagraphs, the world's largest, were then under construction by the Westinghouse Electric Corporation at Sunnyvale, California. The instruments were used for solar research programs conducted by HAO, which at that time was affiliated with Harvard University, Harvard College Observatory, and the University of Colorado.

This remarkable eclipse experiment -- the most advanced of its kind at that time -- studied the spectrum of elements present in the solar chromosphere with unprecedented height discrimination and high spectral resolution. The spectra provided the first experimental evidence for the newly developed concept of non-local thermodynamic equilibrium conditions in the solar atmosphere. Results from the experiment formed the basis for numerous publications at HAO and elsewhere in the 1953 - 1960 period and, in fact, provided the impetus for HAO to develop into a broad, research-oriented institution.

In 1956, HAO built the world’s first K-coronameter (the Mk1) and deployed it to Climax. The K-coronameter was designed to view polarized light from the Sun that is scattered in the outer solar atmosphere known as the corona. Light is polarized when many of the light waves vibrate in a preferred direction (determined by the magnetic field) instead of vibrating in random directions. Detection of this polarized, scattered light allowed HAO scientists to measure the brightness of the corona out to greater heights. Climax observations of the corona revealed that the brightness of the corona changed over the 11-year sunspot cycle, with the brightest parts being located over regions where the magnetic field was strongest: sunspots and active regions. HAO scientist, Gordon Newkirk, produced a sophisticated model of coronal density and magnetic field in 1958, based on the interpretation of coronal data from Climax. It remained a standard reference model for many decades. The Climax observatory continued to acquire important observations of the Sun and remained HAO’s primary observing site until it closed in 1972.

HAO took its equipment to Pukapuka in the North Cook Islands to observe an eclipse.

In 1960, NCAR began construction operations in Boulder, Colorado. The building was designed by the architect I. M. Pei who decided not to compete with the scale of the Rockies but to make a building that was without conventional scale. Pei designed NCAR to impinge minimally on the vegetation and topography of Boulder’s Mesa by returning to elemental forms of sheer walls and unfinished concrete the color of the mountains. The National Center for Atmospheric Research (NCAR) was dedicated in Boulder Colorado on May 10, 1967.

An interior view of MLSO's dome showing the tracking spar holding the Mk1 instrument.

This eclipse photograph was the first to be made with the Newkirk camera that contained a special filter to offset the rapid change in brightness of the solar corona with height. It allowed scientists to record the solar corona for the first time out to nearly 2 million miles (4 ½ times the radius of the Sun) using a single exposure setting. The two teams acquired data that yielded information needed to construct the densities and temperatures in the various bright white structures, known as streamers, visible in the eclipse image. The team was surprised when the results showed that the properties of the different streamers sometimes varied significantly from one streamer to the next. It pointed to the need for more detailed observations throughout the solar atmosphere to understand these variations. The Newkirk coronal camera continued to produce some of the most spectacular and useful pictures ever taken of the white-light corona at eclipses for the next 30 years (see the HAO Eclipse page).

Roger Kopp and Jack Gosling working on an instrument for the 7 March, 1970 eclipse in San Carlos Yautepec, Mexico.

Skylab was the United States' first space station (the first ever space station was the Soviet Salyut 1). Skylab was a 77-ton outpost launched on May 14, 1973 on a modified Saturn V rocket from Kennedy Space Center (formally Cape Canaveral). It remained in Earth orbit from 1973 to 1979 and was visited by crews three times between 1973 and 1974. They reached the station by a Command/Service Module (CSM) launched atop the smaller Saturn IB. Skylab program objectives were twofold: To prove that humans could live and work in space for extended periods, and to expand our knowledge of solar astronomy well beyond Earth-based observations. Nearly 300 scientific and technical experiments were performed including medical experiments on humans' adaptability to zero gravity, solar observations, and detailed Earth resources experiments. The astronauts recorded 127,000 frames of film of the Sun, confirming the existence of coronal holes on the Sun, which are sources of the solar wind.

This false-color image of the solar corona was made with the white-light coronagraph aboard the Skylab spacecraft, with the moon (upper left) approaching the sun to create the total eclipse of 30 June 1973. Here, the light from the solar disk is blocked by an occulting disk, which appears as the solid black circle in the center of the field. The black gap at the bottom is the shadow of a pylon, which holds the occulting disk in place. The colors were added to the image by computer processing after the data were analyzed.

In 1957, HAO built the world’s first K-coronameter and deployed it to their observatory at Climax, Colorado. It was able to measure the brightness of the corona at several heights. A major advancement was made in 1979 when a new state-of-the-art K-coronameter, the Mk3, was installed in HAO’s Mauna Loa Solar Observatory. The Mk3 was the first ground-based instrument to produce artificial eclipse images of the corona in white light, acquiring images every 3 minutes during each observing day. It was the only instrument able to routinely record white light images of the very low corona. This was a major breakthrough, providing daily information on the variation of the structure and brightness of the Sun’s corona. The Mk3 recorded hundreds of explosive events known as coronal mass ejections (CMEs), providing information on the formation, acceleration and sources of these events. Mk3 measurements demonstrated that the brightness of the corona varies by nearly a factor of 6 over the 11-year sunspot cycle, attaining its brightest levels at activity.

The K Emission Line Polarimeter (KELP) was built in 1974 by the High Altitude Observatory (HAO) / NCAR in collaboration with the Sacramento Peak Observatory. KELP was designed to measure polarized light from the Sun’s atmosphere. Light is said to be polarized when many different waves of light vibrate along the same direction, instead of in all different directions. In the Sun’s corona, the magnetic field provides the preferred direction to polarize light. By measuring the polarization you can learn about the magnetic field, which is important because the field organizes the structure of the corona and the field can release energy that creates solar activity. KELP made successful observations of the direction of the coronal magnetic field that helped to prove the power of the technique of using polarization. KELP observations became even more informative in 1980 when they were combined with new daily images of the solar corona from the Mauna Loa Mk3 K-coronameter (as shown in the blue/white photo). Scientists could relate the direction of the magnetic field provided by KELP, to the structures of the corona shown in Mk3 images. These data gave scientists a better understanding of the shape of the coronal magnetic field and helped to determine the sources of the solar wind, the continuous stream of particles that escape the Sun and travel throughout the solar system.

HAO/NCAR designed and operated the coronagraph onboard SMM. The coronagraph recorded over 1,300 CME events (such as the one in the above image, top-center) that helped scientists to better understand how these events form by measuring their basic properties and how they relate to other types of solar activity such as flares. The HAO coronagraph was also used to discover ten sungrazing comets belonging to the Kreutz sungrazer group, which formed when a comet broke up several centuries ago. In 1986, the HAO SMM coronagraph pointed towards Halley’s comet as it made its closest approach to the Sun, revealing new information about the conditions in the comet’s head and tail are effected by the solar wind, a steady stream of particles escaping from the Sun (above, lower-right).

Tim Brown is shown with what was called the Redwood Telescope. Its aim was to measure atmospheric scintillation noise in stellar photometry, using the multiple panes of glass as mirrors to feed light from a star to a single 8-inch telescope. Since each pane sees the star through a different volume of atmosphere, the scintillation noise for the sum should be smaller than for the same-size telescope looking directly at the star. The redwood part was designed and built by Lee Lacey.

Spectropolarimetry provides the most complete and detailed measurement and analysis of light, its interaction with matter and information about the state of magnetic fields. It is the study of polarized light in a narrow range of wavelengths that are produced by known states of atoms. One of the most successful HAO spectropolarimeters was the Advanced Stokes Polarimeter (ASP). By all accounts, this instrument ushered in a new era of quantitative, high-resolution vector magnetic field observations. Operated at Sacramento Peak Observatory, it inferred the three-dimensional magnetic structure of sunspots and other magnetic features.

A landmark union joins two key NCAR models, the Thermosphere/Ionosphere/Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) and version 2 of the Community Climate Model (CCM2). The union evolved by 2000 into the Whole Atmosphere CCM (WACCM), that can simulate the Earth's atmosphere from top to bottom.

HAO celebrated its 60th anniversary in style, with Walt Roberts-themed cake and cookies.

(clockwise, from top-left)

The image is a Molleweide projection located just below the solar surface, with yellow/white tones representing warmer plasma and blue/black tones representing cooler plasma. The solar equator is a few Kelvin warmer than the poles in this simulation, while localized spots of cool plasma dot the layer, corresponding to swirling downflow plumes.

Here we see the radial velocity field just below the solar surface in one such simulation, shown in a Molleweide projection. Bright and dark tones denote upflowing and downflowing plasma respectively. An intricate network of strong, narrow downflow lanes blankets the entire surface, often forming localized, swirling plumes.

This ghostly image shows the enstrophy, which is the magnitude of the vorticity vector squared, in a numerical simulation of solar convection. A Molleweide projection is shown near the middle of the convection zone, about 100 Mm below the solar surface. The enstrophy is very intermittent, confined to very strong downflow plumes and lanes which produce vortex rings and sheets through the entrainment of surrounding plasma.

Sunrise is a unique research project designed to capture features on the solar surface as small as 30 kilometers across (about 19 miles), more than double the resolution achieved by any other instrument to date. Carrying the largest solar telescope ever to have left Earth, Sunrise was launched on a gigantic helium balloon larger than a Boeing 747 jumbo jet, from the ESRANGE Space Centre in Kiruna, northern Sweden on June 8, 2009. The total equipment weighed in at more than six tons and reached a cruising altitude of 37 kilometers (23 miles) above the Earth's surface. The observations (an example is show as an inset above) are helping unlock important mysteries about the structure of the Sun's magnetic field and how it creates solar activity that can cause electromagnetic storms in the Earth’s upper atmosphere. It is also designed to study ultraviolet light from the Sun. Ultraviolet light has shorter wavelengths than our eyes can see. The amount of ultraviolet light produced by the Sun varies over the sunspot activity cycle which has implications for climate on Earth. Ultraviolet light does not reach the surface of the Earth but is absorbed in the ozone layer, where it deposits heat. Sunrise was carried high enough up to detect ultraviolet light carrying out the first ever study of small-scale bright magnetic structures on the solar surface in an important range of ultraviolet light. Sunrise is an international collaboration involving NCAR, NASA, Germany, Spain, Sweden, Lockheed Martin Corporation and the University of Chicago.

In 2010, an HAO-built Fabry-Perot interferometer was installed in Palmer Station, Antarctica (64S, 64W), with funding from the American Recovery and Reinvestment Act of 2009. The instrument measures upper-atmospheric winds by observing the Doppler shift of nightglow emissions. The wind measurements help scientists understand the cause of unusual patterns of the ionosphere like the Weddell Sea Anomaly, where the ionospheric density is greater at night than at day during the summer. The instrument filled a critical data gap.