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The First Scientific Flight and Observations of the 50-mm Balloon-Borne White-Light Coronagraph

Kaifeng Kang, Min Huang, Yang Liu, Jun Lin, Tengfei Song, Xuefei Zhang, Dayang Liu, Tao Zhang, Yan Li, Jingxing Wang, Mingzhe Sun, Mingyu Zhao, Guangqian Liu, Xianyong Bai, Lidong Xia, Yu Liu

TL;DR

The paper reports the first science flight of the 50-mm BBWLC balloon-borne white-light coronagraph developed by Yunnan Observatories and partners to observe the K-corona from 1.08 to 1.50 solar radii. It details the optical design, mechanical structure, stray-light control, and the data-processing approach, followed by a report of the October 2022 flight from Dachaidan that yielded 17,100 frames, with polarization data obtained for three angles due to a polarizer-wheel fault. Polarization analysis reveals a southwestern coronal streamer in pB images, which is cross-validated against K-Cor and AIA observations to confirm authenticity. The study demonstrates the feasibility of near-space white-light inner-corona observations from China, identifies dust- and hardware-related limitations, and outlines future improvements and opportunities for electron-density mapping and coronal-magnetic-field studies when combined with velocity measurements.

Abstract

A 50-mm balloon-borne white-light coronagraph (BBWLC) to observe whitelight solar corona over the altitude range from 1.08 to 1.50 solar radii has recently been indigenously developed by Yunnan Observatories in collaboration with Shangdong University (in Weihai) and Changchun Institute of Optics, Fine Mechanics and Physics, which will significantly improve the ability of China to detect and measure inner corona. On 2022 October 4, its first scientific flight took place at the Dachaidan area in Qinghai province of China. We describe briefly the BBWLC mission including its optical design, mechanical structure, pointing system, the first flight and results associated with the data processing approach. Preliminary analysis of the data shows that BBWLC imaged the Kcorona with three streamer structures on the west limb of the Sun. To further confirm the coronal signals obtained by BBWLC, comparisonswere made with observations of the Kcoronagraph of the High Altitude Observatory and the Atmospheric ImagingAssembly on board the Solar Dynamics Observatory. We conclude that BBWLC eventually observed the white-light corona in its first scientific flight.

The First Scientific Flight and Observations of the 50-mm Balloon-Borne White-Light Coronagraph

TL;DR

The paper reports the first science flight of the 50-mm BBWLC balloon-borne white-light coronagraph developed by Yunnan Observatories and partners to observe the K-corona from 1.08 to 1.50 solar radii. It details the optical design, mechanical structure, stray-light control, and the data-processing approach, followed by a report of the October 2022 flight from Dachaidan that yielded 17,100 frames, with polarization data obtained for three angles due to a polarizer-wheel fault. Polarization analysis reveals a southwestern coronal streamer in pB images, which is cross-validated against K-Cor and AIA observations to confirm authenticity. The study demonstrates the feasibility of near-space white-light inner-corona observations from China, identifies dust- and hardware-related limitations, and outlines future improvements and opportunities for electron-density mapping and coronal-magnetic-field studies when combined with velocity measurements.

Abstract

A 50-mm balloon-borne white-light coronagraph (BBWLC) to observe whitelight solar corona over the altitude range from 1.08 to 1.50 solar radii has recently been indigenously developed by Yunnan Observatories in collaboration with Shangdong University (in Weihai) and Changchun Institute of Optics, Fine Mechanics and Physics, which will significantly improve the ability of China to detect and measure inner corona. On 2022 October 4, its first scientific flight took place at the Dachaidan area in Qinghai province of China. We describe briefly the BBWLC mission including its optical design, mechanical structure, pointing system, the first flight and results associated with the data processing approach. Preliminary analysis of the data shows that BBWLC imaged the Kcorona with three streamer structures on the west limb of the Sun. To further confirm the coronal signals obtained by BBWLC, comparisonswere made with observations of the Kcoronagraph of the High Altitude Observatory and the Atmospheric ImagingAssembly on board the Solar Dynamics Observatory. We conclude that BBWLC eventually observed the white-light corona in its first scientific flight.

Paper Structure

This paper contains 12 sections, 8 equations, 10 figures, 1 table.

Table of Contents

  1. Introduction
  2. Coronagraph
  3. Optical System Design of BBWLC
  4. Mechanical Structure Design of BBWLC
  5. Stray Light Detection
  6. BBWLC System and Its First Flight
  7. BBWLC System
  8. First Flight
  9. Data processing and Results
  10. Polarized Brightness
  11. Comparison of BBWLC Images with K-Cor and AIA Images
  12. Discussions and conclusions

Figures (10)

  • Figure 1: Light path of BBWLC. Sunlight enters the coronagraph from the left.
  • Figure 2: (a) Two-dimensional diagram of the mechanical structure of the BBWLC. (b) The corresponding three-dimensional perspective view of BBWLC.
  • Figure 3: (a) Image for the results of inspecting stray light of the BBWLC before its launch. (b) Variations of the stray light strength in units of 10$^{-6}$$\text{B}_{\odot}$ versus the azimuth at three locations of 1.1, 1.3 and 1.5 solar radii from the center of the Sun. The sudden drop between azimuths of 300$^{\circ}$ and 320$^{\circ}$ results from the block of the light by the supporter of the occulting disk.
  • Figure 4: The predicted stray light contributions from diffraction, O1 ghost, surface roughness, and surface contamination. From 2012SPIE.8444E..3ND.
  • Figure 5: The sketch depicting the basic structure of the BBWLC system that includes a gondola, theodolite and coronagraph.
  • ...and 5 more figures