DFM Engineering, Inc.
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NJIT Solar Telescope
 
 

big bear solar observatoryThe New Jersey Institute of Technology's (NJIT) new 1.6-meter unobstructed aperture solar telescope - the largest of its kind in the world - is now operational. The telescope was officially dedicated on October 3, 2009 at the Big Bear Solar Observatory. This DFM telescope is said to be the pathfinder for all future, large ground-based telescopes.

The Big Bear Solar Observatory (BBSO), is located at Big Bear Lake, California high in the San Bernardino Mountains. The observatory is built out into the lake on a causeway so is surrounded by water. The water stabilizes the atmosphere causing the images of the sun to be much improved which is essential for the primary interests of measuring and understanding solar complex phenomena.

new solar telescopeDr. Frank Melsheimer and the DFM Engineering staff designed the telescope, the thermal control system, and coordinated the NST installation. DFM worked with the BBSO director, Dr. Philip Goode and the project manager, Mr. Roy Coulter. Also involved were Dr. Jeffrey Kuhn, associate director, Institute for Astronomy at the University of Hawaii, and Dr. Buddy Martin, of the Steward Observatory Mirror Laboratory, University of Arizona.

The primary mirror for the new solar telescope uses a 1.6-M diameter segment of a much larger parabolic mirror. This allows an unobstructed aperture to reduce scattered light in the image. The mirror was polished and tested at the Steward Observatory Mirror Laboratory, University of Arizona.

To accommodate the New Solar Telescope, the observatory was first remodeled with a new and larger dome, a reworked concrete pier, and a new instrument floor level. To control the temperature environment inside of the dome, the BBSO staff designed and built a dome ventilation system employing a wind-gate and exhaust system. The system maintains the same temperature inside and outside the dome and clears concentrations of heat in and around the optical paths.

The off-axis New Solar Telescope mount and the Optical Tube Assembly (OTA) was designed and manufactured by DFM Engineering. Ian Huss of DFM led the building and installation of the telescope. Mr. Huss was also a guest speaker at the dedication ceremony. Manufacturing documentation (including subtitled photos) can be reviewed both on the DFM Engineering NJIT Solar Telescope link and BBSO web site.

DFM engineers implemented a closed-cycle, chilled-air system as part of the telescope mount to limit so-called "mirror seeing". The chilled air flows over the surface of the mirror sweeping away turbulent cells and directly cooling the primary mirror on the front surface and on the back surface. Even with the "air conditioning" of the primary mirror, after a day of observations the mirror must be cooled overnight to ensure that it is somewhat cooler than ambient in the morning. Controlling the temperature of the primary mirror is a key design issue for this large-aperture solar telescope.

DFM Engineering designed and built the optical support structure which includes active back supports for the large, but very thin primary mirror. The back supports consist of 36 counterweighted levers with integrated active actuators that can bend out low-order aberrations in the mirror, such as those due to figuring errors, gravity effects, and thermal effects.

In May of 2009, researchers achieved what is called first scientific light, which denotes the telescope is operational. "Seeing first light was a great moment because the team at BBSO finally knew that its big white machine works as we had planned," said Dr. Goode.

sun turbulent granular field

Top photo: Sun with planet Mercury crossing its face. The small black dot at the top of the Sun is Mercury.
Bottom photos: Shots of the sun in hydrogen-alpha light through the 20 cm full-disc telescope. The left-hand image is a normal contrast image. The right-hand image, acquired on a different day, has the contrast enhanced by removing the limb darkening.

Dr. Goode and the BBSO research team were able to extract some unique images.

"Our prized first image shows the Sun's ever-present, turbulent granular field with its largest granules being about the size of Alaska," Goode said.

"The Sun is now in a state of prolonged magnetic inactivity, perhaps the longest such time in a century. The new telescope is ideal for studying the Sun as it rises from this strange state of quietude," he added.

The NST has three times the resolution of the one it replaced which will enable Goode and other scientists to probe the fundamental scale of the Sun's dynamic magnetic fields. These fields are of great interest to solar physicists because they can cause magnetic storms (solar flares and coronal mass ejections) that destroy satellites and disrupt the power grid and affect telecommunications.

The telescope is now in its commissioning phase, in which more sophisticated observations are made possible with the implementation of advanced instruments. These include adaptive optics to correct for atmospheric distortion and hardware to measure magnetic fields in visible and infrared light.

"We are already seeing images offering a better understanding of the Sun," said Goode. "With this instrument, we should be able to have a better understanding of dynamic storms and space weather, which can have dramatic effects on Earth."

To achieve its full powers, at least 3 more years of work will be needed to bring online ever more sophisticated hardware for observing the Sun.

The DFM Engineering team is very excited to be an integral part of the Advanced Technology Solar Telescope (ATST) project of the National Science Foundation.

 

NJIT New Solar Telescope Manufacturing Documentation

BBSO Latest Halpha Images

Association of Universities for Research in Astronomy (AURA)