660, e.g., fastened to the top panel 625 of the sensor body 660. The shell 205 is rotatable around the axis A relative to the housing 110, along with the sensor body 660.

The shell 205 may have radially symmetric shape, e.g., a cylindrical shape. The shell 205 can include a cylindrical portion 640 and an end portion 645. The end portion 645 can be flat and can have a circular shape. The end portion 645 can be attached, e.g., fastened, to the top panel 625 of the sensor body 660. The shell 205 defines the axis A. The lower edge 210 may have a circular shape. The cylindrical portion 640 can have a cylindrical shape defining the axis A, which is vertical. The cylindrical portion 640 can have a constant circular cross-section extending upward along the axis A from the lower edge 210 to the end portion 645. The shell 205 is open at the lower edge 210, thereby permitting airflow into the sensor unit 115 and permitting attachment of the sensor unit 115.

The shell 205 includes a plurality of slits 665. The slits 665 extend through the cylindrical portion 640 and are elongated parallel to the axis A. The slits 665 can be positioned radially outward from the thermal fins 635 and are elongated parallel to the fins. As described below, the slits 665 permit airflow into the shell 205 to exit from the shell 205.

The sensor windows 615 can be recessed from the shell 205. The sensor unit 115 can include window recesses 650 extending from the sensor window 615 and from the respective wall 620 radially outward to the shell 205. The window recesses 650 can include passages 655 positioned to direct airflow entering the shell 205 across the sensor window 615. For example, the passages 655 can be positioned in the first direction of rotation of the sensor body 660 from the respective sensor windows 615, i.e., as the sensor body 660 rotates, each passage 655 leads the respective sensor window 615. The passages 655 can extend vertically for a height of the respective sensor windows 615.

With reference to FIGS. 7A-C, the lower edge 210 of the shell 205 is positioned radially inside the aperture 305 relative to the axis A. The lower edge 210 may be positioned at a same height as or below the aperture 305 relative to the axis A. The shell 205 extends above the aperture 305, i.e., above the highest point of the housing 110. The lower edge 210 may be positioned slightly below the aperture 305, and most of the shell 205 is exposed above the housing 110. Positioning the lower edge 210 below the aperture 305 can reduce airflow escaping while flowing from the housing 110 to the shell 205.

The aperture 305 and the lower edge 210 define the gap 710 extending around the axis A. The gap 710 is the shortest distance separating the aperture 305 and the lower edge 210. The gap 710 may have a constant width extending around the axis A. The gap 710 may be radial and/or axial relative to the axis A. For example, a radial distance from the aperture 305 to the lower edge 210 relative to the axis A may be constant around the axis A, and an axial distance from the aperture 305 to the lower edge 210 relative to the axis A may be constant around the axis A.

The gutter 230 is elongated along the aperture 305 and along the lower edge 210 of the shell 205. The gutter 230 is positioned directly below the lower edge 210 relative to the axis A, i.e., straight downward. The gutter 230 includes a channel 715. The channel 715 has a u- or v-shaped cross-section that follows the lower edge 210 of the shell 205. The channel 715, specifically the cross-section of the channel 715, extends from radially inside the lower edge 210 to radially outside the lower edge 210 relative to the axis A, as well as from radially inside the aperture 305 to radially outside the aperture 305 relative to the axis A. A radially outer edge of the channel 715 can be flush against the lower surface 905 of the housing 110 at or radially outside of the aperture 305 relative to the axis A. The position and shape of the gutter 230 helps the gutter 230 catch fluid, e.g., rain or washer fluid, draining from an outside surface of the cylindrical portion 640 of the shell 205.

Returning to FIGS. 3 and 4, the housing 110 includes at least one drain hole 315, e.g., four drain holes 315, positioned to receive fluid from the gutter 230. The drain holes 315 extend radially outward relative to the axis A from the gutter 230. The drain holes 315 extend from the lower surface 905 of the housing 110 at the gutter 230, i.e., from inside the housing 110, to the upper surface 310 of the housing 110, i.e., to outside the housing 110. Fluid can flow from the gutter 230 through the drain holes 315 and down the housing 110 toward the roof 130 of the vehicle 100.

With reference to FIGS. 7A-C, the brush 705 is fixed to one of the housing 110 (e.g., the aperture 305) or the sensor unit 115 (e.g., the lower edge 210 of the shell 205). The brush 705 extends across the gap 710 toward the other one of the housing 110 or the sensor unit 115 (e.g., the other one of the aperture 305 or the lower edge 210). The brush 705 may be elongated along a circular path following the gap 710 around the axis A and centered on the axis A. Accordingly, the brush 705 may be elongated circumferentially relative to the axis A along the aperture 305 and along the lower edge 210. The brush 705 may be positioned directly above the gutter 230, as shown in FIG. 7A, or the brush 705 may be positioned in the gutter 230, as shown in FIGS. 7B-C.

The brush 705 includes a base 725 and a plurality of the bristles 720. The brush 705 is attached by the base 725 to the one of the housing 110 or the sensor unit 115. The bristles 720 each extend from one end held by the base 725 to a free end. Each bristle 720 may be elongated in a direction perpendicular to a respective tangent to the circular path along which the brush 705 is elongated, e.g., in a radial and/or axial direction relative to the axis A. The direction of elongation may be noncircumferential relative to the axis A. The bristles 720 extend across the gap 710 from the one of the housing 110 or the sensor unit 115 toward the other one of the housing 110 or the sensor unit 115, e.g., the other one of the aperture 305 or the lower edge 210 of the shell 205. For example, the bristles 720 may extend from the aperture 305 toward the lower edge 210 of the shell 205. The gutter 230 may be positioned directly below the bristles 720 relative to the axis A.

With reference to