Dr. Alex Shlanta Astronomical Observatory
Visit to Arecibo Observatory 7-31-07
Thursday, July 31, 2007
by Alex Shlanta
Arecibo Observatory website
Photos courtesy of the NAIC - Arecibo Observatory, a facility of the NSF.
On 20 July 2007 while on vacation I visited Arecibo Observatory. The following discussion is some of my personal reflections from this experience.
The Observatory is located in the western Karst topology region of Puerto Rico. It is the home of the world's largest single dish radio telescope. The receiving dish is located in a large reshaped sinkhole. The facility is operated by Cornell University and supported by the National Science Foundation. The observatory was completed in 1963 and upgraded in 1973 and 1993. The main reflector dish has a diameter of 305 meters (1,000 feet) and covers an area the equivalent of 26 football fields. Suspended 450 feet above the dish is the 6-story dome containing the instrument's Gregorian reflector system. This platform hangs in midair from 18 cables, strung from three reinforced concrete towers. 5 miles of 1-inch thick cables and 25 miles of 1/4-inch thick cables provide physical support. The moveable Gregorian dome has two reflectors and contains a radar transmitter and microwave receiver as well. The system also has a Doppler capability. Originally operating at 430 Mhz, the system with its upgrades now operates in the range 300 MHz to 12,000 MHz.
Early efforts with the telescope were associated with looking at the Earth's upper atmosphere and the solar system. The Ionosphere was studied looking at its structure, geomagnetic disturbances, temperature, wind velocity, electric potential, composition, density, electric and magnetic fields, and aurora. Thunderstorms and lightning were investigated as well. For the solar system emphasis was put on looking at the surface of the Moon, Mercury, Venus, Mars, and the rings of Saturn.
For Mercury it was found that its rotation rate was 59 days verses the 88 days as originally thought. The cloud veil surrounding Venus was penetrated and a 243-day retrograde rotation was found. Further, Venus was found to be a ferocious place and certainly not habitable as originally thought. Preliminary data from the Arecibo telescope inspired the further spacecraft visits to Venus. Jupiter's red spot was found to be a source of high radio energy. The ring structure of Saturn was mapped using the telescope.
For the solar system there continues to be emphasis at Arecibo on finding and tracking asteroids in space that could be potential hazards to the Earth, a very important function. Meteors are tracked in their path through the upper atmosphere. Further, the telescope helps guide spacecraft through the solar system to intercept other planets, asteroids, and comets and determine the best places to land on these.
In outer space a great deal of effort has been spent on finding and studying pulsars, rapidly rotating neutron stars, that emit strong pulsed radio waves from near their magnetic poles. Most of the pulsars we know about were discovered from Arecibo Observatory. Quasars, central regions of young galaxies with black holes emitting an enormous amount of radio energy continue to be studied. These Quasars are way out beyond 10 Billion Light Years and are receding at a rate of greater than 95% the speed of light.
Galaxies continue to be studied at Arecibo. It was found that these galaxies are more massive than thought originally and consist of much "dark matter" which cannot be seen optically. Galaxies in the early stages of evolution have been studied exhibiting extended gas haloes that may be the precursors of the disks of present-day galaxies such as our Milky Way. Maps have been made of three-dimensional distributions of galaxies in space as well.
Radio spectroscopy is used to look at low temperature chemistry in space. Such materials as alcohol, formaldehyde, and carbon monoxide have been found. Gas clouds in other galaxies are investigated as well as interstellar gas clouds in our galaxy. SETI, Search for Extraterrestrial Intelligence, continues to be an ongoing effort with the Arecibo telescope.
The future of the Arecibo Observatory is in jeopardy and this has me concerned since it would be criminal to lose the capability of this telescope. The troubles seem to be related to being in compliance with the government mandate against lead based paints. The large reflector dish needed to be scraped and repainted with a price tag of $3.5 million attached. The parts to be painted are 500 feet above ground level so it is no easy task. The process of painting the telescope is being finished up right now. There have been no observations with the telescope while the reflector is being painted. When the repainting is complete it will need a great deal of calibration before it becomes operative again. In the meantime the NSF almost closed down the facility in the Spring 2007. Several influential citizens of Puerto Rico banded together and fought in support of the facility so it would not be closed. However, in the meantime the staff was cut by 75% and the observatory presently is in limbo.