Spacecraft Model

Introduction

The JUICE Spacecraft model can be useful for a number of different tools and purposes; from PR usage to an introductory step to the spacecraft and its operations or as an input for different applications such as Thermal or Electromagnetic Coupling simulations, ray tracing calculations, FOV or sensor obstruction analysis, S/C Attitude, Solar Array, MGA, and SWI orientation verification etc.

For that purpose the SOC provides a simplified S/C CAD model based on the final complete CAD model provided by Airbus Space to ESA on 2022-10-10. This simplified model preserves all the required details for such applications, in addition the model is provided in accessible formats, such as OBJ in order to prevent the burden to have to use proprietary software such as Catia or Solidworks.

Note

The relationship and description of the materials associated to the surfaces of the model is missing. The SOC currently does not have this information.

Model Contents

The model is split in different components that are provided in separated files. The list provided below indicates the components and the files that are located within:

  • S/C Bus with Optical Bench, HGA, and structure with MLI

    • juice_sc_bus

  • S/C Bus Internal Structures

    • S/C Central cylinder juice_boxes

    • S/C Tanks, Thrusters, and pipes juice_boxes

    • S/C -X and +X Panel Vaultsm juice_boxes

  • Solar Arrays

    • juice_sc_samy

    • juice_sc_sapy

  • MGA Dish and Antenna Pointing Mechanism

    • juice_sc_mga_apm

    • juice_sc_mga_dish

  • RIME antenna

    • juice_sc_rimemx

    • juice_sc_rimepx

  • Mag Boom with J-MAG and RPWI components

    • juice_sc_mag

    • juice_sc_rwi

    • juice_sc_scm

  • Langmuir Probes

    • juice_sc_lpb1

    • juice_sc_lpb2

    • juice_sc_lpb3

    • juice_sc_lpb4

  • Individual Instruments, some with radiators

    • juice_sc_gala

    • juice_sc_janus

    • juice_sc_jmc1

    • juice_sc_jmc2

    • juice_sc_majis

    • juice_sc_swi

    • juice_sc_uvs

    • juice_sc_pep_jdc

    • juice_sc_pep_jei

    • juice_sc_pep_jeni

    • juice_sc_pep_jna

    • juice_sc_pep_nim

    • juice_sc_str1

    • juice_sc_str2

    • juice_sc_str3

Model Formats

The S/C elements of the S/C model are provided in three different formats:

  • OBJ: The standard and popular Wavefront OBJ file format. The OBJ file format can encode surface geometry of a 3D model, using a polygonal mesh and/or freeform geometry using any of a number of techniques to define curved surface patches:. For JUICE it includes geometric vertices, texture coordinates, vertex normals and polygonal faces in ASCII text format (includes MTL and PNG files for textures).

  • SPICE DSK: A direct conversion of the OBJ file to a SPICE Digital Shape Kernel adept to be used in SPICE applications as an extended body. For more information see the NAIF DSK Required Reading.

  • 3DS: 3D Studio Format compatible with SPICE-Enhanced Cosmographia. It is a simplified conversion of the OBJ files to make it compatible with Cosmographia.

Individual models are provided for each element in OBJ format whereas the DSKs and 3DS integrate components based on SPICE and Cosmographia needs. In addition in the location of the OBJ directory a PNG of each component to facilitate its visualization. Note that for some OS systems OBJ files can be easily previewed.

Please note that the S/C Bus internal structures are not available in DSK format as they are not considered to be subject of SPICE calculations, instead they are offered as OBJ files and are also availalbe as 3DS in order to be able to be visualized with Cosmographia if the S/C bus is hidden (cosmos/models/juice_boxes.3ds).

Warning

ESA provides an additional JUICE S/C model for PR purposes in the ESA SciFleet portal. This model is out of date, will not be updated and should not be used.

Model Distribution

The S/C Model is currently included as part of the SPICE Kernel data set and therefore is available from either:
Within the SPICE Kernel data set each file is located as described hereunder:

  • OBJ files are under: juice/misc/models. S/C model elements follow the juice_sc_<component>.obj convention, there is also a textures subdirectory)

  • DSK files are under: juice/kernels/dsk. The directory has an explanatory README file. DSK files are included in the meta-kernel but might not be configured out-of-the-box for all applications.

  • 3DS files are under: juice/misc/cosmo/models. These files are only considered for SPICE Enhanced-Cosmographia

S/C OBJ Parts Location

Given that the spacecraft components are provided in separate files for the OBJ and DSK files, if one wants to assemble the complete model, the position of each element with respect to the JUICE S/C reference frame origin needs to be known.

The JUICE S/C origin is defined as the launch vehicle interface point, located at the separation plane between the spacecraft and the launch adapter, in the centre of the launch adapter (namely close to the S/C bottom at the main engine.)

The location of the OBJ (and DSK) components origin with respect to the S/C reference frame (SPICE frame JUICE_SPACECRAFT) is currently provided by the SPICE Kernel: juice/kernels/spk/juice_struct_v19.bsp (or a later version). The location can then be retrieved with SPICE or by looking at the comments of the binary file. For convenience the location of the different components is provided hereunder:

+----------------------+--------+--------+--------+
| SPICE Component Name | X (m)  | Y (m)  | Z (m)  |
+======================+========+========+========+
| JUICE_SA+Y           |  0.019 |  1.000 |  1.652 |
| JUICE_SA-Y           |  0.019 | -1.000 |  1.652 |
| JUICE_MAG_BOOM       |  1.380 | -0.857 |  0.168 |
| JUICE_MGA_APM        | -1.398 | -0.893 |  3.442 |
| JUICE_MGA            | -1.290 | -1.739 |  3.327 |
| JUICE_STR-OH1        |  1.503 | -0.548 |  2.411 |
| JUICE_STR-OH2        |  1.495 | -0.585 |  2.820 |
| JUICE_STR-OH3        |  1.495 | -0.299 |  2.641 |
| JUICE_JMC-1          |  1.458 | -0.425 |  0.955 |
| JUICE_JMC-2          | -0.021 |  1.058 |  3.624 |
| JUICE_NAVCAM-1       |  0.902 | -0.424 |  3.364 |
| JUICE_NAVCAM-2       |  1.106 | -0.563 |  3.364 |
| JUICE_GALA           |  0.991 |  0.058 |  3.444 |
| JUICE_JANUS          |  1.073 |  0.524 |  3.502 |
| JUICE_MAJIS          |  1.399 |  0.234 |  3.222 |
| JUICE_PEP_JDC        |  1.373 |  0.182 |  0.217 |
| JUICE_PEP_JNA        | -0.247 | -0.978 |  3.793 |
| JUICE_PEP_NIM        | -0.116 | -0.644 |  3.911 |
| JUICE_PEP_JEI        | -0.479 | -0.686 |  3.875 |
| JUICE_PEP_JENI       |  0.300 | -0.784 |  3.640 |
| JUICE_RIME+X         | -0.647 |  0.910 |  3.544 |
| JUICE_RIME-X         |  0.614 |  0.800 |  3.544 |
| JUICE_RPWI_LPB1      |  1.384 |  1.134 |  2.281 |
| JUICE_RPWI_LPB2      |  1.455 | -1.162 |  3.207 |
| JUICE_RPWI_LPB3      |  1.455 | -1.162 |  0.247 |
| JUICE_RPWI_LPB4      | -1.379 |  1.143 |  2.336 |
| JUICE_RPWI_RWI       |  6.775 | -0.857 | -6.495 |
| JUICE_RPWI_SCM       |  6.579 | -0.857 | -6.252 |
| JUICE_SWI_FULL       |  1.424 | -0.379 |  3.558 |
| JUICE_UVS            |  1.430 |  1.141 |  3.191 |
+----------------------+--------+--------+--------+

The algorythm to extract this information from the SPICE Kernels is available in the following Python Notebook: JUICE S/C Components Positions.