Where is NASA located? How can I send them letters?
NASA has at least five different regional facilities. Off the top of my head, Goddard Space Flight Center with locations in Maryland and New York City; Huntsville, AL; Houston: Although Caltech and JPL are technically not NASA, JPL personnel (in Pa lo Alto, CA) is responsible for managing many NASA probes, and Lunar and Planetary Science Laboratory at the University of AZ in Tucson, AZ has a similar arrangement NASA. That's five different locations right there, and you'll probably find more on NASA's web pages. I'm not including Michoud in New Orleans East, because I don't know it anything significant is happening at Michoud right now, and NOE is quite a commute from my New Orleans house in Metairie. The people I used to know who lived in NOE, my soul sister's in laws, moved to Metairie after Katrina. The surge from the lake (Lake Pontchartrain) flooded their house to the ceiling. Yes, the house has been sold and is now occupied. one of the few on that block that were occupied in January, 2009.
You really should figure out exactly WHO you want to write to at or associated with NASA. If they are associated with a particular university, check the faculty or staff web pages of that university and you'll very likely be able to find their e-mail address. You may have to skim through faculty and staff listings of several schools and/or departments before you find the particular person you are looking for.