Hi Josh, Thomas, and Brittany!
That is a great question! My colleagues here at the University of Iowa are working on hardware projects for sounding rockets and new NASA satellites, so I do see a quite a bit of the interaction between scientists and engineers. This interaction takes place on different levels, throughout the various phases of a mission. Some space scientists have backgrounds in both space science research and electrical engineering or computer science, so they can fufill a dual role in mission development.
During the planning phase, scientists and engineers here at the University of Iowa work together to propose instrument designs for a particular NASA mission, or they may even write a proposal for an entire spacecraft or sounding rocket. Together, the scientists and engineers consider what types of instruments (plasma wave instruments, electric field antennas, particle detectors, imagers, etc.) will be included in the mission. The scientists and engineers need to work closely with one another, because they also need to consider things like how much power will be available on the spacecraft, how heavy each instrument can be, if the instruments will interfere with one another, and how long the instruments can be expected to function. They also need to determine what kind of orbit a satellite will need to have, or plan the trajectory of a sounding rocket.
If NASA accepts a proposal for a satellite instrument or sounding rocket, then the scientists and engineers will work together to build and test the instruments they described in their proposal. In addition to working with engineers and electronics technicians, scientists will also work with the machinists who will make the parts for the instruments. My boss is preparing to launch a sounding rocket to study the aurora borealis this winter. The machine shop in our department built the components of the particle detectors for his rocket. An electronics technician assembled the power supplies and electronics for the particle detectors under the direction of a scientist. I am currently helping another scientist test the particle detectors for the rocket. It's very interesting work!
Once all of the instruments are built and tested, NASA engineers will integrate them into the spacecraft or rocket that will be launched. The engineers will carefully test the completed spacecraft or rocket to make sure there are no problems and it is ready for the launch.
After a satellite is launched, scientists need to work with engineers to operate the spacecraft and make sure that the data are properly received on the ground. If something goes wrong with the spacecraft while it is in orbit, the scientists and engineers will work together to come up with a solution that ensures that the mission will be able to continue operating for as long as possible.
There are a few details that I left out, but this is basically how scientists and engineers work together on a NASA mission.
To learn about some of the spacecraft instruments built at the University of Iowa, try this site: http://www-pw.physics.uiowa.edu/plasma-wave/home.html
Kris