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: 10/4/2001 at 13:43 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 330.000 m3 - SF3-11.82-.8/.8-NHR
Balloon serial number: W11.82-1E-26
Flight identification number: 501N
End of flight (L for landing time, W for last contact, otherwise termination time): 10/4/2001 at 21:37 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 8 h 30 m
Landing site: 18 miles WSW of CHildress, Texas, US

The balloon was launched by dynamic method using launch vehicle (Big Bill) on October 4h 2001 at 13:43 utc

Float altitude was achieved at 15:20 utc

The payload was cut down at 21:37 utc and landed at 22:05 utc

• 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