The Balloon-Borne Investigation of Temperature and Speed of Electrons in the Corona (BITSE): Mission Description and Preliminary Results

We report on the Balloon-borne Investigation of Temperature and Speed of Electrons in the corona (BITSE) mission launched recently to observe the solar corona from approximate to 3 Rs to 15 Rs at four wavelengths (393.5, 405.0, 398.7, and 423.4 nm). The BITSE instrument is an externally occulted single stage coronagraph developed at NASA's Goddard Space Flight Center in collaboration with the Korea Astronomy and Space Science Institute (KASI). BITSE used a polarization camera that provided polarization and total brightness images of size 1024x1024 pixels. The Wallops Arc Second Pointer (WASP) system developed at NASA's Wallops Flight Facility (WFF) was used for Sun pointing. The coronagraph and WASP were mounted on a gondola provided by WFF and launched from the Fort Sumner, New Mexico station of Columbia Scientific Balloon Facility (CSBF) on September 18, 2019. BITSE obtained 17,060 coronal images at a float altitude of approximate to 128,000 feet (approximate to 39 km) over a period of approximate to 4 hrs. BITSE flight software was based on NASA's core Flight System, which was designed to help develop flight quality software. We used EVTM (Ethernet Via Telemetry) to download science data during operations; all images were stored on board using flash storage. At the end of the mission, all data were recovered and analyzed. Preliminary analysis shows that BITSE imaged the solar minimum corona with the equatorial streamers on the east and west limbs. The narrow streamers observed by BITSE are in good agreement with the geometric properties obtained by the Solar and Heliospheric Observatory (SOHO) coronagraphs in the overlapping physical domain. In spite of the small signal-to-noise ratio (approximate to 14) we were able to obtain the temperature and flow speed of the western steamer. In the heliocentric distance range 4-7 Rs on the western streamer, we obtained a temperature of approximate to 1.0 +/- 0.3 MK and a flow speed of approximate to 260 kms(-1) with a large uncertainty interval.

Automated summary

The BITSE mission utilized a balloon-borne instrument to observe the solar corona, providing crucial data on equatorial streamers and temperature flow rates. By comparing with existing SOHO data, it was found that BITSE observations were consistent with known properties of the solar corona.