(How we'll keep our stories safe in our lunar payload)
Question from Don Krieger: I have a question about longevity of the memory card which will be used. Will the ambient radiation on the moon degrade and eventually destroy the data on the card? If so, how long and is the card hardened or protected from radiation? Thanks very much for all that you do. Best – Don
Answer from Susan Kaye Quinn: This is an excellent question! I had planned on blogging about this at some point, and here we are. We’ll be using SanDisk’s Extreme microSD card, the most durable of the commercially available ones that I could find.
There are, of course, serious issues with ambient radiation on the moon (or anywhere in space, in particular going through the Van Allen belt on the way there). People who rely on microSD cards for memory in space (for example small satellites) often have software management systems to handle this, with redundant storage and data checks to keep things clean (or repair damage). Some use radiation hardened memory, but that’s expensive and not an option for us (and it’s really just a fancy way to build in redundancies). Many use COTS (commercial off the shelf) cards and either use the software management systems or have short lifetimes and just deal with the damage. Many use COTS and never experience problems, so we’re looking at random radiation damage that’s *possibly* causing damage but not guaranteed, ie it’s at a low enough level that commercial satellites are often using COTS with no problems.
We’re different in that we’re going to be on the Moon for a LONG time (indefinite) and still want the card to be accessible.
I considered using TWO cards, a physical redundancy that would cut our risk in half. I’m afraid it won’t fit in the container with the other items I want to include. Still waiting to see the stackup to see if I can make that work. I may send everything to Astrobotic and say “if you can make the two cards fit, go for it!” It will be close.
My current plan is to include one (or two) SDcards, a physical paper mini-book with a listing of the website and the authors’ names, and a thin piece of sheet metal with the website. The WEBSITE on earth is the actual backup. It will have pages that describe what people put on the payload, plus links to the authors’ main book on the manifest. If our intrepid moon archeologists discover our payload and the SDcard is damaged (there is a possibility that SOME of the data will remain even if SOME is damaged), then they will see the website address and at least have access there to the stories, and the stories behind the stories, that were originally placed in the payload. I will be putting website maintenance in my will, so this will hopefully outlive me.
There’s one more thing we have going for us, and this is the most helpful of all: our payload will be buried inside a lander with other payloads. Lunar radiation is not so severe that it can penetrate more than a few thin metallic sheets, and we’ll have a lot of armor all around us. That’s the thing most likely to protect our stories.
Thanks for your concern! Like I said, I planned to blog about this at some point. Now, I guess I have!
Sue