Welcome back to the competition formerly known as Space Security Challenge 2020, now HackASAT.
Well, it's actually still known by Moth. I just wanted to change the intro because they're going
to get pretty repetitive. I'm your host, Jordan Wines. The game has been a little bit slower this
hour, but that makes sense because teams are starting to get into the harder challenges.
As a reminder, teams are currently working on two separate challenges.
First, the on-orbit challenge involves them designing a payload that will execute a moonshot,
taking a picture of the moon from an actual orbiting satellite. While that challenge won't
show up on the scoreboard with points, it is a pass-fail challenge. Only teams that score within
a time window will be eligible for podium placement and the related $50,000, $30,000,
and $20,000 prizes. Since there's a lot of data being displayed on our octagon scoreboard,
otherwise known as that thing you're looking at when it's not my face on this YouTube feed,
here's a quick primer on some of the elements. First, the display on the left shows a scoreboard
breakdown that breaks down each team's points earned per challenge, shows the total score,
and includes a log of recent solves and messages sent from each team to their Flatsat.
Note that the message contents have actually been sanitized to not give away answers,
but you might find some other things there instead.
On the right scoreboard, you'll see the time of the teams, you see the score of the teams over time.
Right now it's skewed a little bit to the left, but as the game progresses, it'll stretch out
and we'll see how they do on each of these new challenges. Finally, each team has a dedicated
panel with a main view and three supplementary views. Technically, we can change the supplementary
views, but right now the main view shows a team logo with their color, a representation of the
team's Flatsat, including their rotation, position over the earth, and messages sent. Note that the
little pew-pew you see are just for visual effect and not actually representative of actual messages
being sent. On the graph right now on the right, excuse me, the three graphs on the right, the top
graph is yaw, the middle graph is angular velocity, and the bottom graph is total messages, all done
over time, which makes for a nice overview of the different activity from each team's Flatsat.
Remember, you can vote to control which of these views you're looking at in the virtual environment
inside of the Stardome. That feed doesn't cut over these live updates and always shows the octagon.
While we wait on our teams to continue to solve these challenges they're working on,
now's a great time to introduce another segment we call Space Talk. If, like me, you're a hacker
who might know about computers but is ignorant of what goes into making code run in space,
there's a lot of new things to learn. Our first Space Talk episode is about how to keep track of
time in space. So what time is it in space? Well, that's a complicated question. For the astronauts
on the International Space Station, and for most orbiting satellites, they run on Coordinated
Universal Time, or UTC. It's not actually a time zone but rather a time standard that just so
happens to be the same as GMT. It's used to prevent time zone confusion and give a standard time to
reference. But for astronauts especially, it's just a number. On the International Space Station,
the sun rises and sets about every 90 minutes, so there isn't any relationship between the sun
and what time it is that's meaningful to the astronauts. Satellites are the same way. Time is
primarily used to inform them when to execute commands and perform operations. Universal time
is just a reference number that's easy to relate back to your local time. But that's not the only
time that's used for space applications. UTC is not an exact accounting of the passage of time,
but rather strives to stay aligned with the rotation of the Earth, because it's primarily
people on Earth that are using it. Earth's rotation is both irregular in the short term
and slowing down permanently in the long term. Earth days are getting about 1.6 milliseconds
longer every single day. This isn't in any way noticeable in daily life, but can be very
significant over time. As a result, we use a different time scale when dealing with orbital
motion. Orbital motion doesn't care about the Earth's rotation at all. It must be extremely
precise because of the massive distances involved. The most common time standards used are Julian
date and terrestrial time, which are both entirely independent of Earth's rotation. To give an idea
of just how different these time scales can be, over the last century between 1900 and 2000,
universal time was about 64 seconds slower than terrestrial time. It's a tiny difference to us,
but when you're dealing with precise predictions over millions of miles, it gets very significant.
And that's the key. What time it is in space isn't important so you can look at the clock on the wall
and know if you need to go to bed. It's important so you can know where you are and know where
things are. Everything in space is constantly moving, orbiting one object or another. Telling
where it's located is intrinsically linked to what time it is. This gets to our next question.
How do you tell where something is in space? As I said before, everything in space is constantly
moving and orbiting around something else. All this motion is primarily controlled by gravity.
So to know where something is right now, we use where it was at some time in the past,
and we predict where it is now based on the laws of gravitational motion. Now you might ask,
how do I tell you where it is or even where it was? On earth, I could tell you where to go based
on your address or some landmark, and these are useful frames of reference that we can use to
fully communicate where something is. In space, there are an infinite number of reference frames
that we can use, but we also have an added complexity. Since again, everything is moving
all the time, to have a frame of reference, we need to incorporate time. There are several
different ways of describing where things are, but we typically focus on two reference frames.
One, what's easiest for us to use. For example, if I want to take a photo of the moon, I would
want to know where the moon is in relation to where I'm going to be when I have my camera.
Two, what's easiest to calculate. Orbital math is hard and many times impossible, so
picking a reference frame that makes your calculation as easy as possible is often necessary.
This reference point is usually whatever has the most significant gravitational effect
and ignores all other motion. For satellites, we use earth. We want to know where they are relative
to our location on the earth. This frame of reference is called earth-centered earth fix,
or ECEF, as it is rotating with the earth and is fixed to it. It's the same as GPS coordinates,
but it's much, much easier to calculate the position of the satellite when we ignore the
rotation of the earth, which is a different frame of reference called earth-centered inertial,
or ECI. So if I saw where a satellite was in relation to me in the ECEF frame at time t0,
and I need to know where the satellite will be in relation to me in the ECEF frame at time t1,
we actually need to calculate three different steps. One, translate the coordinates I observed
at t0 in ECEF to ECI at t0. Two, translate the orbital motion of the satellite in ECI from t0
to t1, where our calculations are easier. And three, translate the coordinates I calculated at
t1 back to ECEF from ECI. Steps one and three both require translating between these coordinate
frames ECEF and ECI. So how do we do that translation? Here is where we now introduce
the idea of an epoch. An epoch is a point in time that we use as a reference to translate between
these types of frames. Specifically, we use the J2000 or Julian date 2000 epoch to translate
between ECEI and ECEF as we set the ECI reference frame to be the same as the ECEF at that time.
That way we can calculate the translation between them by calculating how much the earth has
rotated since Julian date 2000. This is a simplification of the constant translation
and calculation done throughout satellites, space technology, and astronomy. But that is
why time and space are both extremely important and highly dependent on really what you're looking
to do with them. Thanks to Jess Coffey for putting those videos together. That one was epic. Now this
was going to be where I signed off for this update, but as we were live, PFS actually jumped up on the
scoreboard yet again, solving challenge two. This means that we can now move on to exposing
all teams to challenge three. Challenge three. Here's what we know. With the repair complete
on the GNC, the satellite has stopped spinning, but we still can't communicate with the payload
module or operate the imager. We have to ask ourselves, what else did they damage on this
satellite? The challenge? Teams must restore communication with the payload module so we
can get it working again. This has been our last hourly update for the day. I'm looking forward to
seeing everyone back here at 4 p.m. Pacific, 7 p.m. Eastern for a daily recap of all that's happened so far.