SIHLA - Spatial/Spectral Imaging of Hydrogen Lyman Alpha

摘要

SIHLA is a small satellite mission proposed as a Mission of Opportunity to NASA for flight on the same launch opportunity as the NASA IMAP mission. SIHLA is a free-flyer that is carried into a transfer orbit on the ESPA-Grande ring. The SIHLA spacecraft flies independently to the L1 point where it will orbit and perform its science mission. From there, SIHLA will map the distribution of H in the heliosphere. From the L1 point, outside of the Earth's atmosphere and H exosphere, SIHLA is able to map the sky without the absorption of the terrestrial H. SIHLA takes an existing scanning imaging spectrograph (SIS) and adds a Hydrogen Absorption Cell (HAC). The SIS produces spectral images from 115nm to 180 nm - including the H Lyman a line (at 121.6nm)- at all points in the sky. SIHLA uses the HAC, and our observing geometry, to sample, over time, the entire H Lyman a lineshape. The line-of-sight integrated lineshape contains, within it, information on the density, temperature and velocity of Heliospheric H. Remote sensing measurements from SIHLA, and the contributions of our international team, ensure the continuation of the legacy of the SOHO/SWAN mission into the next solar cycle. SIHLA's enhanced capabilities will provide new insights into the Heliospheric boundary and the processes that shape the distribution of H within the heliosphere. These new and unique observations from SIHLA, together with observations from IMAP and Voyager 2, will lead to a revolution in our understanding of the ISM-Heliosphere interaction.