BepiColombo’s science teams have reported instrument checks following the separation of its Mercury Transfer Module on September 3, 2026. An ESA mission update published on October 6 describes tests that became possible after the transfer hardware no longer obstructed parts of the observing instruments. The work concerns preparation for Mercury operations, rather than the start of the planned orbital science program.
The joint European and Japanese mission carries two scientific spacecraft: ESA’s Mercury Planetary Orbiter and JAXA’s Mercury Magnetospheric Orbiter, known as Mio. Their different instruments are intended to investigate the planet and its surrounding environment. The latest results provide evidence about the health and configuration of selected instruments after the interplanetary journey. They do not establish that Mercury orbit insertion or the subsequent science observations have already occurred.
One of the tested instruments is the BepiColombo Laser Altimeter, or BELA. The University of Bern’s account describes initial laser activation on September 14. Engineers began with a short firing sequence, evaluated the returned instrument data, and then increased the operating duration. This staged procedure limited the duration of an unexpected condition before the team had evidence that a longer run was appropriate.
Those laser pulses were directed into open space, rather than toward Mercury’s surface. The test could establish properties of the instrument’s operation without producing a planetary elevation measurement. This is a useful distinction for interpreting descriptions of activation or first light. An instrument can demonstrate that its source, detector, or electronics works before it has observed the scientific target in the intended measurement geometry.
The German Aerospace Center, DLR, describes a longer BELA test on September 15 in its instrument-performance report. The laser operated for about 21.5 hours and emitted more than 700,000 pulses. A small portion of emitted light was directed to the receiver, allowing the team to assess instrument condition without a reflecting planetary surface. DLR reported that the results supported preparation for Mercury observations.
A laser altimeter estimates distance by measuring the travel time of a pulse sent toward a surface and reflected back to its receiver. Interpreting that distance as surface elevation also requires knowledge of the spacecraft’s position and pointing. BELA’s intended measurements concern the planet’s shape and surface elevations. Repeated observations can also contribute to studying surface deformation and rotation. These measurements address physical properties that cannot be determined from a single ordinary photograph. Their scientific use will depend on the observing orbit, instrument calibration, and interpretation of the returned measurements together with other mission information.
The Mercury Radiometer and Thermal Infrared Spectrometer, or MERTIS, underwent a different check. Its normal planet-facing optical path had been obstructed by the transfer module. After separation, the team could compare observations through that path with observations through its calibration opening. DLR reports a 22-hour test on September 15 and an initial comparison showing little or no sensitivity loss relative to a cold ground calibration performed in 2013.
That comparison is evidence about instrument response under specified conditions. It does not mean every eventual measurement has already been calibrated or that uncertainty has disappeared. An infrared instrument must distinguish information arriving from its target from effects associated with the instrument’s own temperature and operating state. Tests across changing thermal conditions help establish how those factors affect the data.
A third result concerns SIMBIO-SYS, an integrated imaging and spectroscopy instrument. The Italian Space Agency’s October update reports that its three optical channels operated in their final configuration on September 15. The initial acquisitions confirmed functioning systems, with additional adjustment of operating conditions still planned. The report identifies stereoscopic imaging, higher-resolution imaging, and visible and near-infrared measurements as complementary functions.
Stereoscopic imaging observes terrain from different directions so that researchers can derive information about its shape. Higher-resolution images examine smaller surface features. Spectral measurements divide reflected light into wavelength ranges, providing information relevant to surface materials. Combining these observations can help relate a feature’s appearance and geometry to its composition, rather than interpreting each type of evidence separately.
New Space Economy’s background on the European–Japanese Mercury mission describes the broader purpose of using two orbiters. A surface-focused measurement and an observation of Mercury’s space environment address different questions. Their value comes from relating those questions through appropriately timed observations and analysis. The current instrument checks support that eventual research program, but remain engineering preparation for it.
The change from cruise configuration to science configuration matters because spacecraft hardware is arranged differently for different mission phases. Equipment needed to transport the orbiters can obstruct an instrument’s intended viewing direction. Removing that equipment permits checks that were previously impossible in the same configuration. A successful earlier test cannot automatically replace a later test after the physical arrangement has changed.
Calibration is also distinct from simply receiving data. A functioning detector can return numbers, but scientific interpretation requires understanding what those numbers represent and how their uncertainties arise. Comparisons with known reference conditions help establish that relationship. Cross-checks between complementary instruments can later reveal whether an apparent feature is consistent across measurement methods or requires further investigation.
The mission’s remaining sequence includes orbital operations before the main observing program. The Italian Space Agency lists the beginning of Mercury orbit insertion for November 21, 2026, followed by separation of the two science orbiters on December 9–10. The main science phase is planned for April 2027. These dates describe planned events, not completed outcomes or guarantees that every subsequent activity will occur on schedule.
The September checks establish specific evidence of instrument operation after years in space and after a change in spacecraft configuration. The remaining task is to complete arrival operations, establish the intended orbits, and obtain calibrated measurements of Mercury. Scientific conclusions about the planet must follow those observations; successful instrument activation is a necessary preparation for that work, rather than a substitute for it.
