Description of the Hayabusa AMICA Images with Geometry Backplanes bundle V1.0 ============================================================================= Bundle Generation Date: 2021-11-16 Peer Review: Neese_Richardson_Mueller_Migration Discipline node: Small Bodies Node Content description for the Hayabusa AMICA Images with Geometry Backplanes bundle ================================================================================= Note: This bundle was migrated to PDS4 from the PDS3 data set HAY-A-AMICA-3-AMICAGEOM-V1.0. For PDS3 data sets migrated to PDS4, the following text is taken verbatim (except for corrected typos, and adjusted file name extensions) from the data set description and confidence level note of the PDS3 data set catalog file. In these cases, some details may not be correct as a description of the PDS4 bundle. The data files are unchanged but labels with wrong entires were corrected. The HAYABUSA spacecraft is the first mission to have successfully sampled an asteroid, returned in June 2010. This Japanese mission included the Asteroid Multi-band Imaging Camera (AMICA) which imaged the surface of the sampled asteroid. This camera is a charge-coupled device (CCD) camera with a refractive telescope producing an effective field of view of 5.83 x 5.69 degrees. In the course of the mission, AMICA obtained 1662 images which are archived in PDS as Saito et al. (2010). For information about the design, performance and calibration of the AMICA camera, see Ishiguro et al. (2010). The AMICA Derived Data Record (DDR) contains geometric information for each pixel of 1339 images that views the surface of 25143 Itokawa. The DDR includes the location of each pixel on the surface of the asteroid, the solar incidence angle, emission angle and phase angle at each pixel when the image were acquired, and data on the local slope relative to gravity, the acceleration due to gravity and the elevation relative to a reference gravitational potential at each pixel, assuming a constant density asteroid. Data ==== These DDR are broken out into 2 groups. A very high quality group (in directory data/ddr_gaskell) where the locations, illumination and geometric parameters for each AMICA pixel are calculated from parameters derived using geometry obtained while constructing the shape model for Itokawa using stereophotoclinometry (SPC) [see Gaskell et al. 2008a,b]. The second set of DDRs is of lesser quality (in directory data/ddr_spice), but remains nevertheless very useful and is derived from geometric information while preparing filtered version 1 of the Hayabusa LIDAR dataset [see Barnouin-Jha et al. (2008); Mukai et al. (2008) for details on how those data were derived]. Both SPC and LIDAR data provide the location of the HAYABUSA spacecraft relative to the asteroid. In the case of the data derived by SPC, SUMFILES are generated that solve for the same data that exists in NAIF SPK and CK kernels, namely the spacecraft trajectory and attitude. These solutions were used the make the SPC derived DDR backplanes. In the case of the AMICA DDRs derived using LIDAR data, the LIDAR solutions were used for the spacecraft ephemeris. These are archived at NAIF as hay_osbj_050911_051118_v1n.bsp. The spacecraft attitude or pointing data was obtained from the current attitude kernels available at the PDS for the pointing data delivered to the PDS by the HAYABUSA project. All the SPICE kernels used are listed in detail in the next Ancillary Data section. The DDRs generated using Stereophotoclinometry are listed in the text file backplanes_filelist_gaskell.asc, while those derived from the SPICE data currently available at the PDS are listed in the file backplanes_filelist_spice.asc. Both these list files are located in the document directory. Also located in the document directory are two pdf files with images of all the backplanes for each of the two sets of images. These files are backplanes_summary_gaskell.pdf and backplanes_summary_spice.pdf. Each of the AMICA DDR files is essentially a 16-layered image cube. The first layer or band of this cube has the pixel values of the original fits images delivered to the PDS by the Hayabusa team. The second, third and fourth layers provide the x, y and z coordinates of each pixel center located on the surface of the asteroid. The prime meridian for Itokawa, which defines the x-axis or zero Longitude of Itokawa, is given by a black boulder observed on the 'head' of Itokawa, and is defined in the Itokawa planetary kernel listed below in the 'Ancillary Data Section'. The x,y,z, locations of each pixel are determined from the intersect of the field of view of each pixel with an Itokawa shape model generated by [Gaskell et al. 2008b]. The fifth, sixth, and seventh layers show the location of this pixel center using latitude, East longitude and radial distance from the center of figure of the asteroid. The eighth, ninth, and tenth layers of the DDR cube give the average Solar incidence, emission and phase angle across each one of the pixels. The eleventh and twelfth layers provide the horizontal and vertical pixel scale of AMICA across the surface of Itokawa. The thirteenth, fourteenth, fifteenth, and sixteenth layers provide the average surface slope relative to gravity, the average elevation relative to gravity, the average gravitational acceleration, and the average gravitational potential at each pixel on the surface of the asteroid. These last four values were calculated using the method described in Cheng et al. (2002) using a constant density for Itokawa of 1.95 g/cc and a rotation rate of 0.000144 rad/s. With this density and rotation rate the gravitational potential on the surface can be computed via integration (see Cheng et al. 2002; Barnouin-Jha et al., 2008 for details). From the resulting gravitational potential, a reference gravitational potential equivalent to a 'geoid' on Earth can be obtained from the area averaged root mean square of this gravitational potential. This reference potential provides the elevation on the surface of the asteroid once divide by the local magnitude of the gravitational acceleration. The density and rotation also provides via integration the magnitude and direction of the gravitational acceleration at the surface. The slope given is obtained by taking the acosine of the dot product of the normal to each plate model facet with the vector describing the direction of the gravitational acceleration at the center of each plate model facet. All the AMICA Derived data records are 32-bit binary images, using the standard PDS image (.IMG) format. They may be read into ISIS version 3.2 using the command pds2isis: 'pds2isis from=st_2445206532_v_ddr.lbl to=6532.cub' This will generate an ISIS cube called 6532.cub. The ISIS package called 'qview' allows you to view the image and any back planes. It should be noted that use of x, y, z locations to analyze Itokawa images is better then analyzing the data using latitude and longitude and radius as more typical when working with planets. This is because there are areas of Itokawa where one latitude and longitude can define more than one asteroid radius. Ancillary Data ============== The Ancillary data used to compute the backplanes for AMICA include several SPICE kernels. All these kernels are available through PDS at htpps://naif.jpl.nasa.gov/pub/naif/pds/data/hay-a-spice-6-v1.0/haysp_1000/data The exact kernels used include : (1) The following leap second kernel (lsk): naif0009.tls (2) The following planetary constants kernel (pck): pck00008.tpc itokawa_gaskell_n3.tpc (3) The following spacecraft clock kernel (sclk): hayabusa.tsc (4) The following frame kernels (fk): itokawa_fixed.tf hayabusa_hp.tf (5) The following instrument kernel (ik): amica31.ti (6) The following ephemeris kernels (spk): de403s.bsp sb_25143_140.bsp hay_jaxa_050916_051119_v1n.bsp hay_osbj_050911_051118_v1n.bsp (7) The following spacecraft attitude kernels (ck): hayabusa_itokawarendezvous_v02n.bc (8) The plate models used for the purpose of determining the DDR backplanes of AMICA have been archived at the PDS (Gaskell et al. 2008b). The shape model closest in resolution to the pixel scale of a particular AMICA image were employed while generating that image's backplane. Coordinate System ================= A planetocentric coordinate system is employed, which is body-centered, using the center-of-figure as the origin. The actual vector from the center of Itokawa to the surface should be primarily employed for scientific purposes because of the important curvature of Itokawa where some locations can possess more than one latitude and longitude. However, latitude and longitude data are also provided, but should be used with caution. The latitude is defined by the angle between the equatorial plane and a vector extending from the origin of the coordinate system to the relevant point on the surface. Latitude is measured from -90 degrees at the south pole to +90 degrees at the north pole. Longitude extends from 0 to 360 degrees, with values increasing eastward (i.e., it is a right-handed coordinate system) from the prime meridian. This coordinate system is preferred for use in navigation and geophysical studies in which, for example, estimates of elevation or gravitational potential are provided (as in the AMICA DDR bands 13-16). References ========== Barnouin-Jha, O., A. Cheng, T. Mukai, S. Abe, H. Naru, R. Nakamura, R.W. Gaskell, J. Saito, and B.E. Clark. Small-scale topography of 25143 Itokawa from the Hayabusa laser altimeter. Icarus 198, 108-124, 2008. Cheng, A.F., O. Barnouin-Jha, L. Prockter, M. T. Zuber, G. Neumann, D. E. Smith, J. Garvin, M. Robinson, J. Veverka, and P. Thomas, Small-scale topography of 433 Eros from laser altimetry and imaging. Icarus 155, 51-74, 2002. Gaskell, R.W., O. Barnouin-Jha, D.J. Scheeres, A.S. Konopliv, T. Mukai, S. Abe, J. Saito, M. Ishiguro, T. Kubota, T. Hashimoto, J. Kawaguchi, M. Yoshikawa, K. Shirakawa, T. Kominato, N. Hirata, and H. Demura, Characterizing and navigating small bodies with imaging data, Meteoritics and Planetary Science, 43, Nr 6, 1049-1061, 2008. Gaskell, R., Saito, J., Ishiguro, M., Kubota, T., Hashimoto, T., Hirata, N., Abe, S., Barnouin-Jha, O., and Scheeres, D., Gaskell Itokawa Shape Model V1.0. HAY-A-AMICA-5-ITOKAWASHAPE-V1.0. NASA Planetary Data System, 2008b. Ishiguro, M., R. Nakamura, D.J. Tholen, N. Hirata, H. Demura, E. Nemoto, A.M. Nakamura, Y. Higuchi, A. Sogame, A. Yamamoto, K. Kitazato, Y. Yokota, T. Kubota, T. Hashimoto, and J. Saito, The Hayabusa Spacecraft Asteroid Multi-Band Imaging Camera: AMICA, Icarus (2010), doi:10.1016/j.icarus.2009.12.035, 2010. Mukai, T., Abe, S., Barnouin-Jha, O., and Cheng, A., Hayabusa LIDAR V1.0. HAY-A-LIDAR-3-HAYLIDAR-V1.0. NASA Planetary Data System, 2008. Saito, J., Nakamura, T., Akiyama, H., Demura, H., Dermawan, B., Furuya, M., Fuse, T., Gaskell, R., Hashimoto, T., Higuchi, Y., Hiraoka, K., Hirata, N., Honda, C., Honda, T., Ishiguro, M., Kitazato, K., Kobayashi, S., Kubota, T., Matsumoto, N., Michikami, T., Miyamoto, H., Nakamura, A., Nakamura, R., Nemoto, E., Sasaki, S., Shinohara, C., Smith, P., Sogame, A., Terazono, J., Tholen, D., Yamamoto, A., Yokota, Y., Yoshida, F., and Yukishita, A., Hayabusa AMICA V1.0. HAY-A-AMICA-3-HAYAMICA-V1.0. NASA Planetary Data System, 2010. Caveats to the data user ======================== Timing Uncertainty ================== The clock aboard Hayabusa possesses an estimated uncertainty of +/- 12 seconds due to a periodicity in the control and operation of the analog signal processing unit. This effect was somewhat remedied by the analysis used by the LIDAR science team. The relative pointing between the ONC-W2 camera and AMICA were statistically adjusted so that a simulated image using the Hayabusa shape model would match the location of Itokawa observed by AMICA. Both data sets suffer from the same timing problem and our approach would thus have minimized their effect over the lifetime of the mission, and these also influence AMICA derived data products. Pixel Location Uncertainty ========================== The Amica Derived Data Records, also possess two levels of quality. The higher quality data are listed in amica_backplanes_file_list_gaskell.txt. For these data obtained while generating the shape model of Itokawa, uncertainties in the location are on the order of 0.2 times the pixel sampling size. At 20km range from the surface of the asteroid this implies an uncertainty in position of 0.5m. At 4 km, this uncertainty measures ~0.1m. The Derived Data products generated combined the LIDAR spacecraft ephemeris solutions and Hayabasa project delivered attitude (listed in backplanes_file_list_spice.asc) uncertainties in pixel location are somewhat larger. At most these can be 10m. However, in general the errors are much less, probably on the order of ~0.5m, based on the excellent match between the location of topography observed on Itokawa with AMICA, and the estimated location of that topography using the combined LIDAR spacecraft ephemeris solutions and the HAYABUSA attitude data. See Barnouin-Jha et al. (2008) for additional details. Limitations =========== The HAYABUSA Derived Data Records were obtained for the majority (81%) of the AMICA images obtained, but not all. This is in part because many of the images were not of Itokawa, or were taken when Itokawa was smaller than a few pixel and the spacecraft was too far for the LIDAR to acquire its surface. In these latter two cases it was impossible to derive the location of the spacecraft relative to Itokawa in any meaningful way and thus obtain a Derived Data Product.