The penetrators are separated from the spacecraft 3 to 5 days prior to the encounter with Mars, and begin their autonomous flight. Probes are transferred into a descent trajectory permitting their penetration to the selected areas of Mars. Probes undergo aerodynamic braking in the martian atmosphere, first using a rigid cone and then an air-inflated braking device, until a given velocity is reached to provide their penetration into the martian regolith. The penetrating part of the probe forebody carrying the scientific and housekeeping instrumentation enters the regolith down to 5-6 m, while the afterbody with the rest of the instrumentation remains on the surface. Scientific measurements begin after penetration.
Information is transmitted to the orbiter.
The primary scientific objectives are to study the vertical structure of the atmosphere, assess the martian climate, and make measurements regarding the internal structure, surface morphology and composition, magnetic field, and seismic characteristics. The two stations on each mission will be separated 3 to 5 days before landing. Sites selected must in the 0 degrees to 55 degreesN zone at elevations below 2 km. Each station is about 1 m in diameter, has a mass of 33.5 kg and a payload mass of 8 kg. Anticipated lifetime on the surface is 700 days.