298 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



completely dark to the eye. As a consequence, much remains to be 

 explored of the heavens when infrared telescopes can be flown from 

 balloons or space telescopes where the telescope can be made very cold. 



BALLOON TECHNOLOGY 



The third possibility for improvement in the operating efficiency 

 and research potential of a telescope has now been opened through 

 advances in balloon teclmology. As mentioned earlier, the efficiency 

 of a telescope increases when the "seeing" image size is decreased. 

 Much effort has been expended in the location of the Palomar and 

 Kitt Peak observatories to find a site with the best seeing conditions. 

 It does not appear that much can be gained in this direction for 

 future telescope locations as long as the terrestrial atmosphere is 

 involved. Only when one can place liis telescope above the atmos- 

 phere does the theoretical resolving power of a telescope become 

 obtainable. Balloon-borne telescopes offer this possibility. 



At balloon altitudes of approximately 80,000 feet there is effectively 

 no seeing disturbance even from direct sunlight on the telescope. Wliile 

 visual observations have been made from balloons, the first successful 

 demonstration of high resolution photography was made with the 12- 

 inch Stratoscope I by Schwarzschild (U.S.A.). This mimanned 

 photographic telescope has taken superb direct photographs of the 

 sun, achieving the full theoretical resolution of the telescope. 



At the present time the 36-inch Stratoscope II system is nearing 

 completion. This instrmnent is large enough to permit the observa- 

 tion of planets, stars, and nebulae, and it is designed to yield a guid- 

 ance accuracy of 0.1 second of arc over extended periods. The 

 achievement of this accuracy should, for instance, permit the solution 

 of the existence or nonexistence of the "canals" on the planet Mars. 

 Other balloon-borne telescopes are planned and several have failed. 

 The launching and operation of as precise an instrument as a telescope 

 from the tenuous platform provided from a balloon are complicated, 

 and the probability for a malfunction of some portion of the system 

 is a real threat to the success of the flight. 



Rockets have been used for the last decade to obtain brief glimpses 

 of the sun and stars from completely above the atmosphere. Even 

 though a rocket-borne telescope has only 3 to 4 minutes of observing 

 time, such a telescope is the only device that astronomers have had to 

 observe the far ultraviolet beyond the atmospheric cutoff at a wave- 

 length of 3000A. Beautiful far ultraviolet spectra and Lyman alpha 

 photographs of the solar disk have been obtained by Tousey (U.S.A.) . 

 The recent flights by Steelier and Milligan (U.S.A.) have observed the 

 spectrum of stars in the far ultraviolet. Since their observations 

 showed that the theoretical predictions of the ultraviolet brightness 

 of the hot O and B type stai*s was incorrect by a large factor much 



