Read the science that did return

Phobos 2’s ISM instrument returned spectra of Mars and Phobos during the orbital phase. Its instrument team describes a scanning method that combined spacecraft motion with a moving mirror to sample neighboring surface patches. An imaging spectrometer records how the received signal varies with wavelength at each sampled location, adding a dimension beyond a simple brightness image.

In an original data-cube exercise, each map location contains five wavelength measurements instead of one brightness value. Two patches can look equally bright in a broad-band picture while their wavelength patterns differ. That difference can guide a composition investigation, but instrument calibration, illumination and other influences must be checked before assigning a material.

ASPERA was designed to measure electrons and ions, while the plasma-wave system investigated a different part of the environment. CNES’s data archive records electric-field and plasma observations during Mars bow-shock crossings, along with ionospheric density measurements using a Langmuir probe. These are results obtained near the spacecraft, not samples collected by a lander on Phobos.

A bow shock is a boundary where an incoming supersonic plasma flow is strongly changed by an obstacle. In an original crossing exercise, a spacecraft records changing particle and field properties as it moves through that region. The position and time of the readings matter: spatial structure and changes over time can both affect a sequence, so one plot does not automatically describe the entire planetary environment.

Three investigations, three kinds of evidence

The returned orbital investigations and the unreached surface experiments belong in separate columns of the mission record. A spectrum acquired remotely is real evidence even though the hopper never landed. Conversely, an orbital result cannot be relabeled as a direct surface measurement simply to complete the planned checklist.

In an original comparison table, retain target, observing platform, measured quantity, acquisition time and processing method. The later HiRISE color view and the earlier ISM spectra can both help study Phobos, but their wavelength coverage, spatial sampling and dates differ. Combine them only with those differences visible; a shared target does not make the products interchangeable.