THE SPACEWIRE INTERFACE FOR HERSCHEL / SCORE SUBORBITAL MISSION Session : SpaceWire missions and applications Short Paper

The HERSCHEL (HElium Resonant Scattering in the Corona and HELiosphere) experiment is a suborbital mission that will observe the Sun and the solar corona in the EUV and in visible light. One of the HERSCHEL instrument is the coronagraph SCORE (Sounding CORona Experiment) aimed at providing images of the extended solar corona in the EUV lines HI 121.6nm and HeII 30.4nm and in the broadband linearly polarized visible light. The two SCORE cameras are developed at the XUVLab of the Department of Astronomy and Space Science of Florence University, in collaboration with the Naval Research Laboratory, Washington, DC. The SpaceWire ESA standard protocol has been selected as the rocket interface. Since HERSCHEL is a suborbital mission and its operation time will be only about 300s, the SCORE SpaceWire interfaces have a customized design to perform specific and automatic procedures. The prototypes and the flight models of the SCORE cameras and the SpaceWire interface have been developed and tested. 1. THE HERSCHEL MISSION HERSCHEL is conceived as a NASA Sounding Rocket Program providing new EUV/UV (H Lyα and HeII Lyα) and visible-light observations of the solar disk and corona [1]. HERSCHEL will investigate coronal heating and solar wind acceleration from a range of solar source structures by obtaining simultaneous observations of the electrons, protons and helium abundances in the solar corona. The mission aims at developing instrumentation that for the first time will directly image and characterize on a global coronal scale the two most abundant elements: hydrogen and helium. This will directly address three outstanding questions in the Sun-Earth Connection theme: 1. Origin of the slow solar wind, 2. Acceleration mechanisms of the fast solar wind, and 3. Variation of Helium abundance in coronal structures. Additionally, HERSCHEL will establish a proof-of-principle for the SCORE Coronagraph, which is in the ESA Solar Orbiter Mission baseline making easier future investigations of CME's kinematics, and solar cycle evolution of the coronal plasma. The HERSCHEL instrument package consists of the HERSCHEL Extreme Ultraviolet Imaging Telescope (HEIT) for on-disk coronal observations and two coronagraphs, SCORE and HECOR (HERSCHEL EUV Coronagraph) for off-limb observations of the corona. The monochromatic H I (121.6 nm) and He II (30.4 nm) images obtained by the coronagraphs will provide simultaneous abundance, densities and velocities diagnostics from 1 R to 3 R . HEIT will obtain the intensity of the resonantly scattered He II line below the field of view of the coronagraphs, as well as the He II disk images necessary for the analysis of the coronal emission. The HERSCHEL instruments will be launched at the end of 2007 with a Terrier-Brant booster drawing a ballistic trajectory with an apogee of 335 km. This altitude is needed to avoid the atmospheric absorption of coronal radiation; because of the ballistic trajectory, HERSCHEL will observe only for ~300 sec, when the rocket will be beyond 250 km of altitude. Due to the short duration of the flight and the relatively small reached altitude, all HERSCHEL instruments must be vibration and vacuum resistant but they do not require a space qualification. 2. THE SCORE INSTRUMENT The SCORE coronagraph consists of an externally occulted, off-axis Gregorian telescope with multilayer coated optics [1]. The coronagraph has a visible (VLD) and an UV (UVD) detectors and it is capable of simultaneous images acquisition in the visible light (VL) and in two UV narrowbands. A filter mechanism (FM) swaps a Aluminium and an Al/MgF2 filter to enable the acquisition of the only HeII Lyα line or of HI Lyα line and visible light images. The two independent SCORE detectors will acquire images simultaneously with the Al/MgF2 filter. The selected detectors for SCORE coronagraph are a CCD camera for the visible channel and an Intensified CCD (ICCD, a CCD coupled with a MCP detector) for UV. The visible detector is an E2V CCD47-2