The atmospheric measurements made by the six Mars orbiters in operation (as of July 2020) significantly improved our understanding of the Martian weather and climate. However, while some of these orbiters will reach their lifetime, innovative and cost-effective missions are requested - not only to guarantee continued observation but also to address potential gaps in the existing observing network. Inspired by the success of the two Mars Cube One (MarCO) satellites we have established a mission concept, which is based on a series of cubesats, carried to Mars and injected into a low-Mars orbit as secondary payload on a larger orbiter. Each cubesat will be equipped with the necessary features for cross-link radio occultation (RO) measurements in X-band. Intelligent attitude control will allow for maintaining the cubesats in a so-called “string-of-pearls” formation over a period of about 150 solar days. During this period, a series of RO experiments will be carried out with the larger orbiter for up to 180 measurement series per day. Due to the specific observation geometry, we will obtain a unique set of globally distributed cross-link occultations. For processing of the observations, tomographic principles are applied to the RO measurements for reconstruction of high-resolution 2D temperature and pressure fields of the lower Martian atmosphere. The obtained products will give an insight into various unresolved atmospheric phenomena - especially of those which are characterized by distinct horizontal gradients in pressure and temperature, e.g. as observed at the day-night terminator, during dust storms, or over complex terrain.