# Insight mission broken-plane maneuver needed?

Will the Insight cruise stage do a broken-plane maneuver at TCM-2 (or 3), or does the Centaur upper stage have plenty of performance (as I suspect) to directly insert this small s/c into the necessary inclination?

Earth and Mars orbit the sun in slightly different inclinations. A "broken-plane maneuver" is an inclination change burn midway through the Hohmann transfer orbit, the minimum ∆V is at the mid-point of the Earth-Mars transfer.

I'm asking if the Atlas V's Centaur upper stage will inject the s/c (space craft) directly into the Martian heliocentric inclination, thereby making the "broken-plane maneuver" unnecessary.

The official 2016 MARS INSIGHT MISSION DESIGN AND NAVIGATION doc does not explicitly answer my question.
https://ntrs.nasa.gov/search.jsp?R=20150016876

Orbital inclination change: https://en.wikipedia.org/wiki/Orbital_inclination_change

• +1 Insight is an upcoming NASA mission, the cruise stage would likely be the transfer between Earth and Mars' orbits, TCMs are Trajectory Correction Maneuvers, s/c is spacecraft, and inclination is, well, orbital inclination. There is even a previous question here titled Broken plane manoeuvre. In what way is this question "unclear" close voter? – uhoh Mar 4 '18 at 9:36
• If you'd like to leave a comment asking "I don't understand these terms, could you edit the question and explain them a bit more for some of us" that would be great. – uhoh Mar 4 '18 at 9:37
• CRM114DiscriminatorYour question is not unclear to many people, but it will be for some. Can you consider editing your question and spelling out the terms to make it easier to read for many more people? Thanks! You might also consider adding an additional link for more background on Broken Plane Manoever and perhaps also a link to this question or the answer there as well. – uhoh Mar 4 '18 at 9:41

## 2 Answers

The official article about the cruise phase does not mention a plane change maneuver.

I actually just asked another question here, about why it launches from the west coast. Apparently it is really light, so much so, that they can launch into a far less than ideal orbit. Knowing that they probably have more then enough fuel left over to do the planar adjustment at launch.

• – uhoh Mar 5 '18 at 15:37

The J2000 longitude of the ascending node for Mars is about 50 degrees. (Earth's inclination is so close to zero in that coordinate system that it's not really important)

When Earth is 50 degrees around from Aries in its orbit or 180 degrees further than that, it's in Mars orbital plane. Those are roughly 50 days past the equinoxes: roughly May 10 and November 10. A launch at those times can go directly into Mars' solar orbit.

Although that lines up with InSight's launch date, note that InSight is not intended to go into Mars' solar orbit: InSight is an impact mission. It needs to get to the right point at the right time with a specific velocity vector, which doesn't have to be entirely tangent to Mars' orbit.