The field of aerospace is a fundamentally interactive phenomenon. On the one hand, due to the complexity of a project referring to it, a meticulous and adapted methodology is required. On the other hand, it is also the result of the work and expertise of an international network. In most cases, a single country cannot carry out a mission in space.
This is why the National Academies Space Studies Council exists. Moreover, during a meeting of this council, a NASA associate administrator for science, Thomas Zurbuchen, spoke about the joint decisions of NASA and ESA (European Space Agency). He said dates as well as modeling for future repatriation missions of samples stored on the Perseverance rover were discussed there.
NASA and ESA resolutions
The original plan was for NASA to lead the launch of the sample recovery lander, and ESA of the orbiter back to Earth in 2026. The process was simple: the lander will collect the samples, which will be subsequently cached by the Perseverance rover which would put them aboard the Mars Ascent Vehicle (MAV) rocket, and the orbiter would carry them to Earth in 2031.
However, it looks like plans have changed. Indeed, Zurbuchen told the Space Studies Board that the two agencies will split the sample recovery lander in two, and that the launch date for the latter two is scheduled for 2028. In addition, they have agreed to launch the Earth Return Orbiter in 2027 and the return of the samples in 2033. Note that for the moment, the question of funding in the face of these changes has not yet been communicated.
Why did the two agencies change their original plan?
Primarily because of an independent review by a panel of experts. In 2020 they suggested postponing the next NASA missions to 2027 or 2028. They also said it was more reasonable to put two landers on the Sample Retrieval Lander spacecraft, one lander to drive the rover and another for the AVM.
Secondly, the decisions of the two agencies were also influenced by the delay experienced by ESA’s ExoMars mission. This delay is due to the suspension of all ESA partnerships with the agency in charge of the Russian civil space program called Roscosmos, a consequence of the invasion of Ukraine by Russia.