COsmic Ray and Solar Particle INvestigation
COSPIN comprises a set of five telescope subsystems with a total of six charged particle telescopes to address a wide range of scientific objectives made possible by a mission to investigate the Sun and the heliosphere in three dimensions.
Low Energy Telescope (LET)
LET measures the flux, energy spectra and elemental composition of solar energetic particles and low energy cosmic ray nuclei from hydrogen up to iron. The instrument covers an energy range from ~ 1 to ~ 75 MeV/n, using a double dE/dx versus E telescope. Comprehensive on-board particle identifier electronics and an event priority system enable rare nuclei to be analyzed in preference to the more common species. Isotope separation for light nuclei such as helium is also achieved.
Anisotropy Telescopes (AT)
The ATs sensor unit consists of two, identical charged-particle telescopes, each with a geometrical factor of 0.75 cm²sr, whose role is to measure the three-dimensional charged-particle distribution in the energy ranges 0.7 to 2.2 MeV for Z ≥ 1, 2.2 to 6.5 MeV for protons, and 3.1 to 23.0 MeV for Z ≥ 2. The three dimensional distribution measurements are achieved by inclining the two telescopes at independent angles (AT1 at 145° and AT2 at 60°) to the spin axis of the spacecraft and sectoring (8 sectors) the data outputs of the telescopes during each spin. Both telescopes have a 70° full-opening angle.
High Energy Telescope (HET)
HET is a large geometric factor cosmic ray telescope that uses particle trajectory determination together with the dE/dx versus residual E technique to measure the energy and identify the mass and charge of cosmic rays. For particles which stop in the detector stack, the telescope provides charge and mass resolution sufficient for studies of the chemical and isotopic composition of cosmic rays from hydrogen through nickel (1 ≤ Z ≤ 28). The trajectory of incident cosmic rays can be determined to an accuracy of better than 1°.
High Flux Telescope (HFT)
The HFT, which is mounted on top of the HET, consists of a single 25 mm² × 18 µm silicon surface-barrier detector, passively collimated by a fan-shaped aluminium collimator to give a viewing aperture of 17° × 60°, with a geometrical factor of 0.033 cm²sr. The collimator imposes a low-energy cut-off of 50 MeV for protons and 5 MeV for electrons incident from outside the viewing aperture.
Kiel Electron Telescope (KET)
The KET telescope is mounted to view perpendicular to the spacecraft spin axis and has an acceptance angle of 44.6° full cone with an auxiliary field of view of 106°. KET is designed to measure electron fluxes between 2.5 and 6000 MeV, and to determine energy spectra in the range 7 - 170 MeV. The telescope also provides measurements of the proton and alpha-particle fluxes in several energy windows between 3 and > 2100 MeV/nucleon. In addition, two low-energy electron and proton channels provide anisotropy information in 8 sectors.
Summary of Objectives
Examples of the COSPIN scientific goals include:
- For energetic charged particles of solar origin, to determine the role of coronal magnetic fields in their acceleration and propagation and to search for the origin of the enrichment of ³He and Fe nuclei observed in some solar particle events
- Using galactic cosmic radiation measurements, to explore the likely reduction or elimination of solar modulation in polar regions relative to the equator, to search for the origin of the anomalous nuclear component, and to determine the nucleosynthetic origins of nuclei at lowest measurable energies
- For energetic nuclei and electrons of interplanetary origin, to study the three-dimensional character of travelling shocks, corotating interaction regions and their associated charged particle acceleration
- As a secondary scientific objective at Jupiter encounter (closest approach 8 Feb., 1992), to characterize the energetic charged particle populations during the first traversal of the dusk side of the Jovian magnetosphere and to search for the mechanism producing the ~10 hour clock variation of Jovian electrons in the interplanetary medium