Activities and Observations during the Europa Clipper Cruise Phase

Launched on 14 October 2024, the Europa Clipper mission represents a pivotal endeavor in planetary exploration, aimed specifically at studying the habitability of Jupiter’s moon Europa. During its cruise phase, the spacecraft will conduct gravity assist maneuvers at both Mars and Earth before arriving in the Jovian system in 2030, where it is scheduled to perform a series of 49 flybys of Europa, along with additional encounters with Ganymede and Callisto. These gravity assists are instrumental in refining the spacecraft’s trajectory and optimizing the calibration of some of its scientific instruments prior to the primary mission phase, underscoring the importance of the cruise period as a preparatory stage for the core observational efforts.

The Mars gravity assist on 1 March 2025 provided an opportunity to calibrate and test three Europa Clipper investigations. First, the Europa Thermal Emission Imaging System (E-THEMIS) thermal instrument acquired data on Mars as a well characterized source, to test an algorithm that corrects a nonlinearity in one of the instrument’s wavelength bands. These observations occurred one day prior to closest approach and near in time when the same region was measured by the THEMIS instrument on Mars Odyssey, which is heritage for E-THEMIS. Second, the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) ice-penetrating radar performed its first comprehensive end-to-end test by operating at closest approach. Due to technical limitations and flow of the flight system integration process, it was not possible to complete such test prior to launch. As a reference for comparison, the Shallow Radar (SHARAD) sounder on the Mars Reconnaissance Orbiter (MRO), which is heritage for REASON, obtained data of the same area 20 minutes later. Finally, the Gravity and Radio Science (G/RS) team tested flyby procedures and processes using the open-loop receivers of the Deep Space Network (DSN). At the time of writing of this abstract, the E-THEMIS and REASON data have not been received due to limitation in the bandwidth of the spacecraft communication. The data are anticipated to be transmitted to ground by June 2025.

The Earth gravity assist will occur on 3 December 2026. This encounter will enable the one and only absolute calibration of the Europa Clipper Magnetometer (ECM) post launch by flying through Earth’s well-characterized magnetic environment. Existing space assets near Earth will also allow for cross-calibration of the Plasma Instrument for Magnetic Sounding (PIMS) through comparison of observed charged particles populations, which are difficult to faithfully reproduce in a laboratory environment prior to launch. Additional instrument operations are presently under discussion. While these observations are not critical to the functioning of the payload, the Earth encounter offers a unique opportunity for the mission operations team to test simultaneous operation of multiple instrument and flight system components in preparation for the primary mission.

Finally, throughout the cruise phase, the mission’s scientific instruments must be exercised periodically to verify functionality and for calibrations purposes. For select instruments, notably ECM and PIMS, these operations enable the collection of complementary data of their heliospheric and magnetospheric environment as the spacecraft transitions through varying interplanetary conditions. The coordination of the Europa Clipper mission with the European Space Agency’s Jupiter Icy Moons Explorer (JUICE) has further created unique opportunities for joint interactive science during the joint cruise phase and beyond. Such collaboration could potentially enhance our understanding of broader dynamics in the solar wind and within the Jovian system while employing complementary observational strategies.

Collectively, the planned and already executed activities during the cruise phase of the Europa Clipper mission will set the stage for detailed analysis upon arrival in the Jovian system, ultimately enhancing our understanding of one of the solar system’s foremost candidates for habitability. At Europa, the anticipated scientific observations will include characterizing the ice shell and subsurface ocean properties, determining the surface and atmospheric composition, and understanding the formation of geological features at the surface. A well-working and fully calibrated payload is a prerequisite for achieving these science objectives and the mission’s overarching goal to investigate Europa’s habitability.