Geometrical Models#

MOS computation is done based on geometrical models largely relying on the SPICE toolkit and kernels, ancillary data in the form of text or binary files. The JUICE SPICE kernel dataset (SKD) contains all the required kernels for modelling and computing the geometry of the JUICE spacecraft, instruments and targets.

../_images/juice_majis_frames.png

Time systems#

(LSK, SCLK)

  • UTC

  • Ephemeris Time (ET)

Solar System bodies ephemeris and shape#

(PCK, SPK, DSK)

Primary targets:

  • JUPITER

  • GANYMEDE

  • CALLISTO

  • EUROPA

  • IO

Secondary targets:

  • MARS

  • VENUS

  • EARTH

JUICE S/C trajectory and pointing#

(SPK, CK)

  • Predicted (for planning)

  • Reconstructed (for data analysis)

MAJIS detectors FOV and pointing#

(FK, IK, CK)

  • Boresight and FOV (FK, IK)

  • MAJIS scanner pointing (CK)

Reference frames#

(FK)

SPICE Frames for the JUICE spacecraft, its structures, and science instruments, as well as for the Ground Earth Stations are defined in Frame Kernel (FK) files. It includes frame definitions for science operations and for data analysis and scientific investigations.

MAJIS frames:

JUICE_MAJIS_BASE        JUICE_SPACECRAFT       FIXED             -28400
JUICE_MAJIS_SCAN        JUICE_MAJIS_BASE       CK                -28401
JUICE_MAJIS_VISNIR      JUICE_MAJIS_SCAN       FIXED             -28410
JUICE_MAJIS_IR          JUICE_MAJIS_SCAN       FIXED             -28420

MAJIS frame hierarchy:

                   "JUICE_SPACECRAFT"
                   ------------------
                           |
                           |<-fixed
                           |
                           v
                  "JUICE_MAJIS_BASE"
                  ------------------
                           |
                           |
                           |<-ck
                           |
                           v
                   "JUICE_MAJIS_SCAN"
          +-----------------------------------+
          |                                   |
          |<-fixed                            |<-fixed
          |                                   |
          v                                   v
"JUICE_MAJIS_VISNIR"                  "JUICE_MAJIS_IR"
--------------------                  ----------------

Dynamic frames#

Dynamic frames are time-dependent reference frames defined via a frame kernel. A “parameterized dynamic frame” is a dynamic frame defined by a formula implemented in CSPICE code and having user-selectable parameters set via a frame kernel. The formula defining a dynamic frame may rely on data from other SPICE kernels, for example state vectors provided by SPK files or rotation matrices from C-kernels or PCK files.

These frames can be used stand-alone, i.e. (1) referring directly to them and assuming they correspond to the JUICE spacecraft reference frame, or (2) in combination with the JUICE spacecraft frames. The latter will allow the user to use the existing alignments and instrument frame definitions to perform instrument specific mission analysis and attitude dependent science opportunity identification.

The following frames are defined in the OPS FK kernel file:

SPICE Frame Name          Long-name
------------------------  ---------------------------------------------
JUICE_EARTH_COMMS         JUICE HGA Earth communications pointing
JUICE_SA+Y_DEFAULT        JUICE +Y Solar Array Default Orientation
JUICE_SA-Y_DEFAULT        JUICE -Y Solar Array Default Orientation

JUICE Nadir orbit-aligned (NOA) pointing:

JUICE_CALLISTO_NOA        JUICE Nadir orbit-aligned pointing @ Callisto
JUICE_EUROPA_NOA          JUICE Nadir orbit-aligned pointing @ Europa
JUICE_JUPITER_NOA         JUICE Nadir orbit-aligned pointing @ Jupiter
JUICE_GANYMEDE_NOA        JUICE Nadir orbit-aligned pointing @ Ganymede
JUICE_MARS_NOA            JUICE Nadir orbit-aligned pointing @ Mars
JUICE_VENUS_NOA           JUICE Nadir orbit-aligned pointing @ Venus
JUICE_EARTH_NOA           JUICE Nadir orbit-aligned pointing @ Earth

JUICE Nadir power-optimized (NPO) pointing:

JUICE_CALLISTO_NPO        JUICE Nadir power-optimized pointing @ Callisto
JUICE_EUROPA_NPO          JUICE Nadir power-optimized pointing @ Europa
JUICE_JUPITER_NPO         JUICE Nadir power-optimized pointing @ Jupiter
JUICE_GANYMEDE_NPO        JUICE Nadir power-optimized pointing @ Ganymede
JUICE_IO_NPO              JUICE Nadir power-optimized pointing @ Io

JUICE Ramming direction (RAM) pointing:

JUICE_CALLISTO_RAM        JUICE Ramming direction pointing @ Callisto
JUICE_EUROPA_RAM          JUICE Ramming direction pointing @ Europa
JUICE_JUPITER_RAM         JUICE Ramming direction pointing @ Jupiter
JUICE_GANYMEDE_RAM        JUICE Ramming direction pointing @ Ganymede

Data visualisation coordinate systems#

Time-series View#

Pointing View#

Map View#

../_images/dataview_crs.png

Geometric search types and constraints#

The SPICE Geometry Finder (GF) subsystem deals with two types of geometric quantities:

  • “Binary state functions”: functions of time that can be “true” or “false.”

  • Scalar numeric functions of time

Numeric searches find times when a scalar numeric quantity satisfies a mathematical constraint. The supported constraints are, the function:

  • equals a specified reference value.

  • is less than a specified reference value.

  • is greater than a specified reference value.

  • is at a local maximum.

  • is at a local minimum.

  • is at an absolute maximum.

  • is at an absolute minimum.

  • is at an “adjusted” absolute maximum: the function is within a given tolerance of the absolute maximum.

  • is at an “adjusted” absolute minimum: the function is within a given tolerance of the absolute minimum.