  Space observatories for gravitational radiation such as LISA are equipped
with dedicated on-board instrumentation capable of measuring magnetic fields
with low-noise conditions at millihertz frequencies. The reason is that the
core scientific payload can only operate successfully if the magnetic
environment meets certain strict low-frequency requirements. With this purpose,
a simplified version of the proposed magnetic measurement system for LISA has
been developed for a six-unit CubeSat, which will make it possible to improve
the technology readiness level (TRL) of the instrument. The special feature of
the experiment is that the magnetic sensors integrated in the payload are
magnetically shielded to low-frequency fluctuations by using a small
cylindrical permalloy enclosure. This will allow the in-flight noise
characterization of the system under the CubeSat orbit environment. Therefore,
a CubeSat platform will offer the opportunity to measure the capability of the
instrument and will guide the progress towards the improved magnetic
measurement system for LISA. This article describes the principal
characteristics and implementation of the CubeSat payload.
