OSO-8 turns out great—Hughes News January 19, 1979 Transcribed by Faith Macpherson

Sun studies ‘oh so’ good

The HAC-built Orbiting Solar Observatory (OSO-8) satellite has been turned off after supplying what NASA scientists consider the most accurate data on the Sun and its functions for three years.

The last of the “sunshine” satellites, which started investigation of the Earth’s nearest star with OSO-1 in 1962, was designed to last one year. It was launched June 21, 1975, from Cape Canaveral, FL.

The spacecraft, designed and built by Space and Communications Group, received high praise for its operations and data returned from NASA officials.

NASA indicated that the Sun-pointed experiments aboard OSO-8 obtained the most accurate observations of the solar chromospheres, the layer of the solar atmosphere just above the relatively cool visible surface of the Sun, and of the transition zone between the chromosphere and the Sun’s extremely hot corona.

“The OSO series has provided a vast wealth of scientific information about the Sun and other celestial objects,” said Roger Thomas, NASA Goddard Space Flight Center OSO-8 project scientist.

“Each of the satellites carried different and succeedingly more accurate instruments to investigate new aspects of the Sun,” he continued.

“The lessons we have learned from 16 years of the OSO mission have been instrumental in the development of new experiments for future studies of the Sun.”

HAC Program Manager Jim Meyer said although OSO-8 was a complex spacecraft, there was little surprise that it continued to work for three years.

OSO-8 carried eight experiments. Two scanned the Sun’s chromosphere to study ultraviolet radiation. The other six made solar and celestial x-ray measurements of the extremely hot and high energy particles in space.

The studies were conducted from OSO-8 as it orbited the Earth from 345 miles up. At this distance, all experiments could be conducted without interference from the Earth’s atmosphere.

NASA Goddard was able to aim OSO-8’s on-board instruments at the Sun with the pointing accuracy of one arc-second, which is one three-hundred-and-sixtieth of a degree. This stability made it possible for the instruments to scan 450-mile wide swaths of the Sun.

The OSO-8 scientific instruments were silenced during the satellite’s 18,072 orbit by a planned radio command sent from Goddard through NASA’s Orroral, Australia, tracking station.

OSO will allow scientists to check into sun’s corona Hughes News June 27, 1975 Transcribed by Faith Macpherson

 Because the sun’s energy gives life to earth, it’s little wonder that man seeks to learn more about an area that has mystified science for centuries.

Scientists will have a chance to scrutinize the sun’s atmosphere with the aid of the Orbiting Solar Observatory (OSO) launched by NASA from Cape Canaveral last Saturday.

The unmanned 2257-pound (1024 kg) spacecraft, designed and built by Space and Communications Group for NASA’s Goddard Space Flight Center in Greenbelt, MD, was launched by a Delta booster into a 343-mile-high (555 km) orbit to circle the earth every 96 minutes for the next year or so.

Primary scientific objective of the orbiting observatory called OSO-I, eighth spacecraft of a series launched since 1962, is to obtain a better understanding of the complex regions between the solar surface and the upper regions of the corona.

In this area, called the chromosphere-corona interface, the temperatures soar from 10,000 to more than 3 million degrees Fahrenheit, creating extremely hot gases that sweep out across 93 million miles of space to continuously immerse the earth and its sister planets in a tenuous solar wind that often creates auroral displays and sometimes disrupts worldwide radio communications.

Some NASA scientists believe the rise in temperature is due to continued agitation of the gases of the corona by shock waves heated and compressed, rising out of the boiling surface of the sun. These sharply defined shock waves, like a thunderclap or the sonic boom produced by aircraft, following one another in rapid succession, could create an accumulated heating effect to raise the temperature in the corona region considerably.

OSO-I will train telescopic instruments on the sun with a pointing accuracy of one arc second, or 1/3600 of a degree, an accuracy similar to a rifle marksman keeping a 10-foot target in his sights over the distance of Boston, MA, to Washington, DC, 400 miles or 643 km.

Pinpoint accuracy of this nature enables OSO to scan areas of the sun’s rim in 450-mile swaths – an area considered small because the sun’s diameter is 864,000 miles.

OSO consists of a spinning section, called the wheel and a stationary platform known as the sail. The sail contains solar cells to provide power and carries two pointing instruments able to scan the sun or point at any position on it. One, a spectrometer from the Centre National de la Recherche Scientifique (CNRS), France, will make fine structure studies of the chromosphere. The other, from the University of Colorado, will take high resolution ultraviolet spectrometer measurements.

Both instruments will scan the sun for other targets of opportunity, such as flares or sunspots.

Six additional instruments mounted in the spacecraft’s wheel, include experiments from Goddard Space Flight Center, University of Wisconsin, Lockheed Missiles and Space Company, Columbia University, and the U.S. Naval Research Laboratory. They will measure solar and celestial X-ray and ultraviolet radiation.

OSO-I is 10 ½ feet (3.2 m) high and 7.2 feet (2.18 m) in diameter. The spacecraft is designed for a one-year life in space.

The project is managed by Goddard, which is also responsible for OSO tracking and data acquisition and the Delta Launch vehicle.