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: 9/26/1994 at 13:01:50
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 N40I-8/8T-11.62
Balloon serial number: R11.62-1-121
Flight identification number: 388N
End of flight (L for landing time, W for last contact, otherwise termination time): 9/26/1994 at 23:00 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): ~ 10 h
Landing site: 15 miles N of Clovis, New Mexico, US

• NASA Balloon Flights (1989-1998) in NASA Historical Data Book, Vol. VII: NASA Launch Systems, Space Transportation, Human Spaceflight, and Space Science, 1989-1998
• Results of the September 26, 1994 Balloon Flight of the Solar Disk Sextant: Implications for the Variability of the Solar Diameter and Oblateness Bulletin of the American Astronomical Society, Vol. 26, p.1377
• Variation of the Diameter of the Sun as Measured by the Solar Disk Sextant (SDS) Monthly Notices of the Royal Astronomical Society, Volume 436, Issue 3, 11 December 2013, Pages 2151-2169