Mission development schedule
A short, intense development schedule tough on all the participants
All space missions are divided up into various phases designated by letters. A project begins with phase A and finishes with phase F, when the spacecraft is decommissioned.
InSight’s preliminary design phase A was kicked off in May 2011 when the mission (at that time known as GEMS) was shortlisted, along with two other projects, as a finalist in the 12th iteration of the Discovery programme. Phase A examines and documents the project’s feasibility. In August 2012, InSight was definitively chosen as the Discovery programme’s 12th mission.
In September 2012, the project moved into phase B, which entails the team in charge of the mission proving that the proposed concept is valid. Next comes phase C, initiated in InSight’s case in June 2013. This is when the definitive version of the probe was designed. Once this final version had been given the green light, manufacturing as such could begin, signalling the start of phase D. This development phase included construction and thorough testing of the various subsystems, and finally their integration to form the final spacecraft.
Once assembled, the probe has to be fully tested once again before being taken to the launch pad for its journey to Mars. Once there, after the routine checks have been carried out and the scientific instruments (SEIS and HP3) have been deployed, the operating phase can begin. Phase E, as this is known, is when the first scientific data is acquired. For InSight, this phase will last at least two Earth years (equivalent to one Martian year). If the systems are still working well at the end of this period, NASA may decide to extend the mission.
A short development cycle
In all, just five years separate the start of phase A in May 2011 and the launch, initially scheduled for March 2016. The InSight mission’s development cycle has obviously been very short, in keeping with all NASA’s Discovery missions.
Keeping to such a tight schedule has been a major challenge for all the teams involved in the mission. Theoretically, the technical risks appeared minimal and the design process looked as if it was going to be seamless. One of the reasons for this is that the InSight lander is almost a carbon copy of the Phoenix probe that successfully landed on Mars in May 2008.
Following in the footsteps of a predecessor having already undergone its baptism of fire and having been able to implement the lessons learned from that mission, it was logical to consider that (almost) everything would go smoothly. This impression was no doubt consolidated by the fact that several components for InSight could be reused from previous missions. This was the case, for example, of the IDA, a robotic arm first used for Mars Surveyor 2001, and the two technical cameras, a colour version of the danger avoidance and navigation cameras used on US rovers Spirit, Opportunity and—more recently—Curiosity.
Yet, as often occurs in the space sector, things did not work out exactly as planned. Even if a mission looks at the outset very similar to a previous attempt, it rapidly becomes unique in its own right.
Indeed, the InSight probe certainly is unique in terms of its payload, i.e. the instruments it is designed to land on Mars. Mission managers had clearly stated from the start that the SEIS seismometer and the HP3 heat flow sensor were going to be the project’s major unknown, the part where risks ran the highest. The future would show that these risks were actually greater than imagined in the case of the seismometer.
The SEIS instrument was not designed specifically for the InSight mission. Its legacy goes back to Mars 96, a mission launched on November 1996 that included two landing capsules containing the Optimism broad band seismometer. Despite the probe’s tragic destiny, crashing into the Pacific Ocean after being unable to break free from Earth’s gravity, development work on the seismometer continued thanks to funding from the French space agency, CNES.
Over the years, the prototypes developed have offered increasingly better performance. An enhanced version was considered for the Netlander mission, unfortunately abandoned in detailed design phase B. A new, even more enhanced model was offered to the European Space Agency for ExoMars, but it was finally rejected, leaving the InSight probe the difficult task of depositing on Mars an instrument that has benefitted from almost 20 years of constant development, and which has crystallized so many of its designers’ hopes and efforts.
Unfortunately, adversity lies in the details, and while the delicate pendulums central to the seismometer were already mature from a technical viewpoint, the difficulties encountered were linked to a part that nobody had really suspected as a possible source of problems: the evacuated sphere. The latter is designed to house the pendulums, offering them an ideal environment in which to work on Mars.
The sphere is crucial to the seismometer’s operation as it both isolates the instrument’s pendulums from the huge temperature differences on Mars and protects them from contamination by particles that could upset their fragile mechanisms. It must remain perfectly sealed at all times, the smallest leak being considered unacceptable.
When the sphere was delivered to CNES in July 2015, a leak was detected. Despite the considerable efforts made by the technical teams to understand and repair the problem, additional leaks occurred, leading NASA and CNES to issue a joint statement on 22 December 2015 announcing the suspension of the March 2016 launch and its possible postponement to May 2018.