Trajectory and ROIs intersections#

traj in roi#

A Trajectory object can be compared with an ROI object to know if, at least, one point of the Trajectory is inside the ROI. For that, you can use the python in keyword between the Trajectory and the ROI:

sc_traj in GanymedeROIs[1, 0, 1]

True

sc_traj in GanymedeROIs[1, 0, 3]

False

The intersection can also be computed for a ROIsCollection:

sc_traj in GanymedeROIs[1]

True

sc_traj in GanymedeROIs

True

In all cases, the results will always be a single boolean.

traj & roi#

Danger

The intersection operators (& and ^) are not commutative.

If you need to compute the actual intersection between the Trajectory and a ROI, you need to use the intersection operator &:

sc_traj & GanymedeROIs[1, 0, 1]

<MaskedSpacecraftTrajectory> Observer: JUICE | Target: GANYMEDE
 - First UTC start time: 2035-06-01T10:32:00.000
 - Last UTC stop time: 2035-06-01T16:44:00.000
 - Nb of pts: 18 (+1,423 masked)
 - Nb of segments: 3

In this case, you will get a MaskedSpacecraftTrajectory object that contains only the portion of the trajectory that intersects the ROI. Here, only 13 points were kept out of the initial 1441.

The intersection also works on a ROIsCollection:

sc_traj & GanymedeROIs[1]

<MaskedSpacecraftTrajectory> Observer: JUICE | Target: GANYMEDE
 - First UTC start time: 2035-06-01T00:33:00.000
 - Last UTC stop time: 2035-06-01T23:52:00.000
 - Nb of pts: 278 (+1,163 masked)
 - Nb of segments: 54

traj ^ roi#

If you need the complementary Trajectory not in the ROIsCollection, you can use the symmetrical difference operator ^:

sc_traj ^ GanymedeROIs[1, 0, 1]

<MaskedSpacecraftTrajectory> Observer: JUICE | Target: GANYMEDE
 - First UTC start time: 2035-06-01T00:00:00.000
 - Last UTC stop time: 2035-06-02T00:00:00.000
 - Nb of pts: 1,423 (+18 masked)
 - Nb of segments: 4

roi & traj#

When you intersect an ROIsCollection you will get a sub-selection of the ROIs that are intersected by the Trajectory:

GanymedeROIs[1] & sc_traj

<ROIsCollection> 12 rois
 - JUICE_ROI_GAN_1_0_01
 - JUICE_ROI_GAN_1_0_02
 - JUICE_ROI_GAN_1_0_04
 - JUICE_ROI_GAN_1_0_05
 - JUICE_ROI_GAN_1_0_06
 - JUICE_ROI_GAN_1_0_08
 - JUICE_ROI_GAN_1_0_10
 - JUICE_ROI_GAN_1_0_12
 - JUICE_ROI_GAN_1_0_13
 - JUICE_ROI_GAN_1_0_14
 - JUICE_ROI_GAN_1_0_17
 - JUICE_ROI_GAN_1_0_19

If you intersect an ROI with a Trajectory, you will get the ROI object itself if the intersection is valid or an EmptyROI if it is not.

GanymedeROIs[1, 0, 3] & sc_traj

<EmptyROI>

Important

If a target attribute is available in the Trajectory and in the ROI, the intersection will also check their values to make sure that they correspond to the same target:

>>> CallistoROIs & sc_traj
<ROIsCollection> No roi

roi ^ traj#

The symmetrical difference can also be reversed to get a ROIsCollection of all the ROI that are not intersected by the Trajectory:

GanymedeROIs[1] ^ sc_traj

<ROIsCollection> 7 rois
 - JUICE_ROI_GAN_1_0_03
 - JUICE_ROI_GAN_1_0_07
 - JUICE_ROI_GAN_1_0_09
 - JUICE_ROI_GAN_1_0_11
 - JUICE_ROI_GAN_1_0_15
 - JUICE_ROI_GAN_1_0_16
 - JUICE_ROI_GAN_1_0_18

fovs & roi#

Caution

The intersection between an FovsCollection and an ROI is not implemented yet. You should use the intersection with the InstrumentTrajectory for now. In that case, the intersection is performed with the instrument boresight.

Representation on a Map#

Using the logical operator you can quickly represent the intersection between the groundtrack trajectory and Ganymede polar deposits (i.e. in the sub-category 1):

fig = plt.figure(figsize=(12, 9))
ax = fig.add_subplot(projection=GANYMEDE)

ax.plot(sc_traj & GanymedeROIs[1], color='r', linewidth=3)
ax.plot(sc_traj ^ GanymedeROIs[1], color='w', linestyle='--')

ax.add_collection((GanymedeROIs[1] & sc_traj)(edgecolors='r', linewidth=3))
ax.add_collection((GanymedeROIs[1] ^ sc_traj)(edgecolors='w', linestyle='--'));

ax.set_title('JUICE groundtrack intersecting the Ganymede polar deposits');
../../_images/16f94e4e841d1152a8acd77eb554de5538ac16f8aa8713f091daee17c026c5d4.png

Export ROI temporal coverage#

Similarly to the Trajectory segments, you can export the intersection between your Trajectory and your ROI/ROIsCollection with the esa.export_timeline() function presented here.