SDS (Solar Disk Sextant)

The Solar Disk Sextant (SDS) is a balloon-borne instrument whose objective is to measure the solar diameter, at different orientations, as a function of time. Results include the solar oblateness, the oscillation spectrum for use in helioseismology, and the rate of the secular variation of the solar diameter. The required instrumentation precision (a few milliarcsec) is attained by means of an objective beam splitting wedge which produces multiples solar images through consecutive reflections.

Balloon launched on: 10/11/1990 at 14:06 utc
Launch site: Scientific Flight Balloon Facility, Fort Sumner, (NM), US  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon SF3-317.60-080-NSCH-02
Balloon serial number: W11.82-1-04
Flight identification number: 299N
End of flight (L for landing time, W for last contact, otherwise termination time): 10/11/1990 at 23:50 utc
Landing site: 13 miles S of Shawnee, Oklahoma, US

• Development of a System for Accurate Forecasting of Solar Activity Annual rept. 15 Oct 1990-14 Oct 1991
• NASA Balloon Flights (1989-1998) in NASA Historical Data Book, Vol. VII: NASA Launch Systems, Space Transportation, Human Spaceflight, and Space Science, 1989-1998
• Preliminary results of a balloon flight of the solar disk sextant Astrophysical Journal, Part 1, vol. 389, p. 447