3:45 PM - 4:00 PM
[PPS07-17] TERRAIN MAP OF ASTEROID RYUGU BY MOSAIC COMPOSITING
Keywords:Hayabusa2, Asteroid Ryugu, Global Terrain Map, Mosaic Compositing
Introduction: Japanese spacecraft Hayabusa2 by JAXA has successfully delivered its sample from the carbonaceous asteroid (162173) Ryugu to the Earth and started its extended mission (nicknamed as Hayabusa2#) to perform a flyby of asteroid 2001 CC21 in 2026 and rendezvous with asteroid 1998 KY26 in 2031 [1]. The Telescopic Optical Navigation Camera (ONC-T) onboard Hayabusa2 observed Ryugu with 7 narrow-band filters ranging from 0.40 to 0.95 μm (ul, b, v, na, w, x, p) [2]. The ONC data products from raw (L2a) to I/F images (L2d) and associated backplane data (L2dbpc) of the surface of Ryugu have been archived through Data ARchives and Transmission System (DARTS) by JAXA [3] and Planetary Data System (PDS) by NASA. Those data also can be found through JAXA Asteroid Data Explorer (JADE; https://jade.darts.isas.jaxa.jp/) developed by [4]. The higher level products, such as photometrically corrected images and mosaic images are still in process and will be released in near future for public use. In this presentation, we will introduce a terrain map product created by projecting ONC v-band images (L2d product) onto the latitude-longitude coordinate and mosaic-compositing them.
Methods: Photometric correction. The backplane data (L2dbpc) was created for each pixel of I/F Image Data (L2d) which includes longitude, latitude, and viewing geometry parameters (incident angle, emission angle, solar phase angle, polygon id of the shape model, and distance from the facet). To make the mosaic composite map seamless and at the same time to preserve the shadows of the terrain, we applied photometric correction especially with a phase function. In this work, we applied an empirical phase function, which are dependent on only phase angles.
Projection & mapping. We projected photometric corrected images based on their backplane data and composited them in chronological order or with the higher resolution image at the top. The terrain map resolution [deg/pix] of projection was defined by the center latitude and the resolution [m/pix] of the field-of-view. For mapping, pixels with shadows at the rim of Ryugu (at i > 70°) were excluded.
The product: We created global and local terrain map products with images observed in proximity phase or in certain operation. Global maps with different solar phase angles were developed. Local maps are prepared for each operation. Fig.1 shows one of the global map products. Map products are in the GeoTIFF format images. GeoTIFF is an image data format include georeferencing information within a TIFF (Tagged Image File Format) file. This allows map products to be overlaid as layers using a GIS application such as QGIS(https://qgis.org/).
Acknowledgments: We used the Hayabusa2 ONC data archived through DARTS (https://www.darts.isas. jaxa.jp/planet/project/hayabusa2/). This work is supported by International Visibility Program of Hayabusa2# project from JAXA.
References: [1] Hirabayashi et al. (2021) Advances in Space Research 68, 1533-1555. [2] Kameda et al. (2017) SSR 208, 17-31. [3] Sugita et al. (2023) Hayabusa2 ONC Bundle, DOI:https://doi.org/10.17597/isas.darts/hyb2-00200, urn:jaxa:darts:hyb2_onc, JAXA Data Archives and Transmission System. [4] Kikuchi et al. (2023) 54th LPSC, #2806.
Methods: Photometric correction. The backplane data (L2dbpc) was created for each pixel of I/F Image Data (L2d) which includes longitude, latitude, and viewing geometry parameters (incident angle, emission angle, solar phase angle, polygon id of the shape model, and distance from the facet). To make the mosaic composite map seamless and at the same time to preserve the shadows of the terrain, we applied photometric correction especially with a phase function. In this work, we applied an empirical phase function, which are dependent on only phase angles.
Projection & mapping. We projected photometric corrected images based on their backplane data and composited them in chronological order or with the higher resolution image at the top. The terrain map resolution [deg/pix] of projection was defined by the center latitude and the resolution [m/pix] of the field-of-view. For mapping, pixels with shadows at the rim of Ryugu (at i > 70°) were excluded.
The product: We created global and local terrain map products with images observed in proximity phase or in certain operation. Global maps with different solar phase angles were developed. Local maps are prepared for each operation. Fig.1 shows one of the global map products. Map products are in the GeoTIFF format images. GeoTIFF is an image data format include georeferencing information within a TIFF (Tagged Image File Format) file. This allows map products to be overlaid as layers using a GIS application such as QGIS(https://qgis.org/).
Acknowledgments: We used the Hayabusa2 ONC data archived through DARTS (https://www.darts.isas. jaxa.jp/planet/project/hayabusa2/). This work is supported by International Visibility Program of Hayabusa2# project from JAXA.
References: [1] Hirabayashi et al. (2021) Advances in Space Research 68, 1533-1555. [2] Kameda et al. (2017) SSR 208, 17-31. [3] Sugita et al. (2023) Hayabusa2 ONC Bundle, DOI:https://doi.org/10.17597/isas.darts/hyb2-00200, urn:jaxa:darts:hyb2_onc, JAXA Data Archives and Transmission System. [4] Kikuchi et al. (2023) 54th LPSC, #2806.