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A Method for On-Orbit Calibration of the VLAST-P Electromagnetic Calorimeter

Jiaxuan Wang, Zhen Wang, Borong Peng, Renjun Wang, Yunlong Zhang, Zhongtao Shen, Yifeng Wei, Dengyi Chen, Xiang Li, Yiming Hu, Jianhua Guo

TL;DR

The paper addresses on-orbit energy calibration of the VLAST-P CsI calorimeter to achieve accurate gamma-ray energy reconstruction. It uses a Geant4-based Monte Carlo framework combined with a geomagnetic backtracing database (GeoMagFilter, built on IGRF-13) to generate realistic MIP calibration signals and applies rigorous event selection and path-length corrections. Key results show energy resolution better than $10\%$ in the range $0.1$–$5$ GeV and linearity deviation below $2\%$, along with a practical calibration plan requiring about $7.5\times10^4$ events across 25 ECAL channels (≈65.7 orbits or ≈98 hours). The approach provides a feasible, data-driven baseline for on-orbit ECAL calibration that supports the full-scale VLAST mission.

Abstract

The Very Large Area Gamma-ray Space Telescope Pathfinder (VLAST-P), as the technology validation satellite for the VLAST mission, is designed to observe high-energy solar bursts on orbit. The CsI electromagnetic calorimeter (ECAL) is one of the key sub-detectors of VLAST-P. To investigate the on-orbit energy calibration method of the ECAL, a Geant4-based simulation of VLAST-P was carried out. The results show an energy resolution better than 10% in the 0.1 to 5 GeV range and a linearity deviation below 2%. A dedicated minimum-ionization-particle (MIP) calibration method was developed to ensure accurate energy reconstruction and to monitor detector stability throughout the in-orbit calibration period.

A Method for On-Orbit Calibration of the VLAST-P Electromagnetic Calorimeter

TL;DR

The paper addresses on-orbit energy calibration of the VLAST-P CsI calorimeter to achieve accurate gamma-ray energy reconstruction. It uses a Geant4-based Monte Carlo framework combined with a geomagnetic backtracing database (GeoMagFilter, built on IGRF-13) to generate realistic MIP calibration signals and applies rigorous event selection and path-length corrections. Key results show energy resolution better than in the range – GeV and linearity deviation below , along with a practical calibration plan requiring about events across 25 ECAL channels (≈65.7 orbits or ≈98 hours). The approach provides a feasible, data-driven baseline for on-orbit ECAL calibration that supports the full-scale VLAST mission.

Abstract

The Very Large Area Gamma-ray Space Telescope Pathfinder (VLAST-P), as the technology validation satellite for the VLAST mission, is designed to observe high-energy solar bursts on orbit. The CsI electromagnetic calorimeter (ECAL) is one of the key sub-detectors of VLAST-P. To investigate the on-orbit energy calibration method of the ECAL, a Geant4-based simulation of VLAST-P was carried out. The results show an energy resolution better than 10% in the 0.1 to 5 GeV range and a linearity deviation below 2%. A dedicated minimum-ionization-particle (MIP) calibration method was developed to ensure accurate energy reconstruction and to monitor detector stability throughout the in-orbit calibration period.

Paper Structure

This paper contains 11 sections, 1 equation, 6 figures, 1 table.

Table of Contents

  1. Space-Based High-Energy Gamma-Ray Observatories
  2. Very Large Area Gamma-ray Space Telescope Pathfinder
  3. Simulation and Performance Evaluation of the VLAST-P Detector
  4. Geant4 Simulation Framework
  5. Detector Simulation SetupDetector Geometry and Materials
  6. Performance and Validation
  7. On-Orbit Calibration of the Electromagnetic Calorimeter
  8. Simulation Methodology
  9. Event Selection
  10. Performance
  11. Conclusion And Outlook

Figures (6)

  • Figure 1: The schematics of the VLAST-P detector system. It inherits the baseline design of the VLAST detector system. ACD serves to distinguish charged particles from gamma rays. The tracker is used to measure the tracks of charged cosmic rays or converted electron pairsTracker is used to measure the momentum of the charged particles either from the deep universe or from the conversion electron pairs. The ECAL is used to measure the energy of particles entering the crystalsECAL is used to measure energy of particles falling into the crystal regions.
  • Figure 2: Exploded 3D visualization of the VLAST-P detector system, generated using Geant4 and JSROOT.
  • Figure 3: Performance of the VLAST-P ECAL: estimated energy linearity and energy resolution.
  • Figure 4: Particle rigidity spectrum from a 20 degrees cone along east direction and west direction
  • Figure 5: Proton MIP response of the VLAST-P ECAL for east- and west-facing configurations
  • ...and 1 more figures