Great moments in coronal observing

Documenting the solar corona is a hallowed part of NCAR history. NCAR’s first director, Walter Orr Roberts, founded HAO and took early coronal measurements from a mountaintop near Climax, Colorado, in the early 1940s. Thus the name “High Altitude Observatory,” which stuck even after HAO moved to Boulder and joined NCAR in 1961. Below are a few highlights of coronal observing from NCAR and elsewhere. (Imagery below from NASA and NCAR.)

1946: The “granddaddy” prominence
Walt Roberts takes a spectacular shot of a prominence, a dense cloud of material emerging from the Sun’s surface, on 4 June using a filter centered on H-alpha (hydrogen) emissions. The image hints at the arch-shaped magnetic structure still being explored by today’s coronal experts.

1964: New heights for white-light imagery
HAO’s Gordon Newkirk and colleagues successfully send a balloon-borne coronagraph to around 30 kilometers (19 miles) in altitude. There, unimpeded by Earth’s lower atmosphere, it obtains the first full-spectrum (white-light) images of the corona ever retrieved outside an eclipse.

1973: Skylab’s big find
From its nine-month tour in space, this human-staffed station collects breathtaking, groundbreaking images of the outer corona, including the first images of coronal mass ejections. HAO furnished Skylab’s white-light coronagraph.

1980: Solar Max goes up
The Solar Maximum Mission satellite (nicknamed Solar Max) was intended to capture a solar cycle at its peak; it gathers data for nearly a decade, notably longer than expected. It obtains the first coronal images to be recorded digitally and telemetered to Earth.

1991: YOHKOH launched
Launched by Japan with U.S. and U.K. collaborators, the YOHKOH satellite studies flares and the solar corona through X rays emitted at various wavelengths by the super-hot solar corona.

1995: SOHO launched
The Solar & Heliospheric Observatory, coordinated by NASA and the European Space Agency, sits over 1.5 million kilometers (950,000 miles) sunward of Earth—one of the Lagrangian points where gravational forces are perfectly balanced.

1996: Fast work from CHIP
NCAR's chromospheric helium imaging photometer (CHIP) debuts atop Mauna Loa. With data every three minutes, CHIP allows scientists to study rapid changes in the chromosphere and to indirectly track the evolution of coronal mass ejections through the study of filament eruptions and waves.

1998: TRACE enters space
NASA’s Transition Region and Coronal Explorer satellite captures the solar corona and transition region (the zone between the corona and the lower solar atmosphere) at unprecedented spatial and temporal resolution.

1998: Mk4 debuts
For nearly 40 years, coronagraphs have kept watch on the Sun from NCAR’s Mauna Loa Solar Observatory. The latest, Mk4, is part of the Advanced Coronal Observing System, an instrument suite that collects data every three minutes from midday to late afternoon as weather permits.