The Dawn Framing Camera

Abstract

The Framing Camera (FC) is the German contribution to the Dawn mission. The camera will map 4 Vesta and 1 Ceres through a clear filter and 7 band-pass filters covering the wavelengths from the visible to the near-IR. The camera will allow the determination of the physical parameters of the asteroids, the reconstruction of their global shape as well as local topography and surface geomorphology, and provide information on composition via surface reflectance characteristics. The camera will also serve for orbit navigation. The resolution of the Framing Camera will be up to 12 m per pixel in low altitude mapping orbit at Vesta (62 m per pixel at Ceres), at an angular resolution of 93.7 μrad px −1 .The instrument uses a reclosable front door to protect the optical system and a filterwheel mechanism to select the band-pass for observation. The detector data is read out and processed by a data processing unit. A power converter unit supplies all required power rails for operation and thermal maintenance. For redundancy reasons, two identical cameras were provided, both located side by side on the +Z-deck of the spacecraft. Each camera has a mass of 5.5 kg.

Geologic map of the northern hemisphere of Vesta based on Dawn Framing Camera (FC) images

“…These observations were acquired during three mission phases corresponding to orbits with different altitudes: an early High Altitude Mapping Orbit (HAMO-1, altitude of 685 km), a Low Altitude Mapping Orbit (LAMO, altitude of 200 km), and a later High Altitude Mapping Orbit (HAMO-2, altitude of 685 km) Russell and Raymond, 2011). FC images were acquired in a frame mode through a panchromatic clear filter and seven narrow-band color filters (Sierks et al, 2011). Clear filter raw images were calibrated, converted to radiometric units and ortho-rectified (Schröder et al, 2013a).…”

“…Clear filter raw images were calibrated, converted to radiometric units and ortho-rectified (Schröder et al, 2013a). From these images several mosaics were produced (Roatsch et al, 2012;Sierks et al, 2011). A mosaic was derived from each mission phase, differing in spatial resolution and illumination conditions.…”

“…Topographic investigations were carried out on Digital Terrain Models (DTM) derived from stereo-photogrammetric and photoclinometry methods (Sierks et al, 2011;Gaskell, 2012;Preusker et al, 2012). The stereo-photogrammetric method relies on the geometric parallax and matching of two to five FC panchromatic images.…”

Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission

“…Spectral modeling of surface spectra acquired by the Dawn mission shows widespread ammoniated phyllosilicates (De Sanctis et al 2015;Ammannito et al 2016) and abundant carbonate deposits in localized areas due to aqueous alteration as well as small spots of water ice in the northern hemisphere (Combe et al 2016). A&A 598, A130 (2017) The Dawn spacecraft (Russell & Raymond 2011) carries three instruments: the Framing Camera (FC, Sierks et al 2011), the Visible and Infrared spectrometer (VIR, De Sanctis et al 2011), and the Gamma Ray and Neutron Detector (GRAND, Prettyman et al 2011). VIR, whose dataset is investigated in this work, is an imaging spectrometer, working in the 0.2-5.1 µm spectral interval, using two channels covering the visible (VIS, 0.25-1.05 µm) and infrared (IR, 1-5.1 µm) ranges, with a spectral sampling of 1.8 nm and 9.5 nm, respectively, and an instantaneous field of view (IFOV) of 250 µrad × 250 µrad.…”

Vesta’s north pole quadrangle Av-1 (Albana): Geologic map and the nature of the south polar basin antipodes

“…Geologic mapping was carried out using mosaics (Roatsch et al, 2012(Roatsch et al, , 2013) of broadband ''clear'' filter images from the Dawn Framing Cameras (FC) (Sierks et al, 2011;Reddy et al, 2012a) and topographic maps constructed with a stereophotoclinometric technique (e.g., Gaskell et al, 2008) and with stereogrammetry (Preusker et al, 2012). The resolution of the digital elevation model (DEM) is 64 pixels per degree, with an estimated 1-r height uncertainty of 8 m. The extensive shadows and large solar illumination angles that are inevitable at high latitudes make FC multispectral images and hyperspectral imaging from the Visible and Infrared (VIR) imaging spectrometer (e.g., De Sanctis et al, 2012a) of limited use in distinguishing color or compositional differences in Av-1.…”