MinXSS-2 delivery date: 2018-08-02

The day is quickly approaching! In just 2 weeks, we’ll be delivering MinXSS-2 to Spaceflight in Seattle. We’ll integrate it into a quad pack of CubeSat deployers and they’ll ship us and a whole lot of other satellites down to Vandenberg for the SSO-A launch on a SpaceX Falcon-9 in late September or early October. If you want the latest on the launch schedule, check spaceflightnow.

In the last couple of weeks before delivery, we’re doing a lot of stuff. After discovering that our flight battery had lost about half of its capacity while sitting on the bench inside MinXSS-2, we decided to build a completely new battery board using fresh batteries just ordered from SparkFun (PRT 13-855). These are nearly identical to the ones we’ve been using on MinXSS, except the form factor became a little narrower and a little longer. We adapt and overcome though! We had to leave out a couple standoffs on our battery board to accommodate the new form factor but we put some extra arathane staking to make sure the batteries can’t shift during vibration testing or launch. The new battery pack is performing exceptionally. We also took the opportunity to double up our battery heaters. We used to have one heater on each side of our battery pack. Now we have two on each side, wired together in series (2s2p configuration). this increases the resistance, which decreases the current (power) draw to run the heaters. But we still get about the same heating effectiveness on the batteries since the heaters now cover nearly the entire surface area of the battery. So the heaters now consume less power for the same effect! We don’t anticipate needing them much on orbit. MinXSS-1 only had them on for << 1% of it’s year on orbit, and spacecraft tend to get warmer the longer they’re up.

We also replaced our command and data handling board after discovering that, during testing, we’d put too much voltage on one of the processor pins. We didn’t see any bad behavior from the processor after this, but we decided to replace the whole thing just to be safe, particularly since we really want MinXSS-2 to last 5 years on orbit.

We finished putting on all the fancy space glue to these new boards and integrated with MinXSS-2. This photo is hopefully our last ever look inside the spacecraft. It’ll be delivered in a couple weeks and be in space in a couple months.

Because of these two major changes to flight hardware, we now need to make sure they’ll be okay in space. So we need to do all of our environmental tests again. That means doing vibration test (2018-07-18), end to end communications testing (2018-07-19), thermal vacuum survival and cycling (2018-07-13 to 26), and a whole lot of smaller tests in between.

So far, everything has been going amazingly. They are extremely long days for James, Robert, and Bennet, but it’s also very rewarding work.

Note that we’re using the @minxsscubesat twitter account a whole lot these days, so we encourage you to check that out for the most up to date news.