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11540	17080	Welcome back to the competition formerly known as Space Security Challenge 2020, now HackASAT.
17100	21720	Well, it's actually still known by Moth. I just wanted to change the intro because they're going
21720	26660	to get pretty repetitive. I'm your host, Jordan Wines. The game has been a little bit slower this
26660	30280	hour, but that makes sense because teams are starting to get into the harder challenges.
30380	34100	As a reminder, teams are currently working on two separate challenges.
34100	41900	First, the on-orbit challenge involves them designing a payload that will execute a moonshot,
41900	46240	taking a picture of the moon from an actual orbiting satellite. While that challenge won't
46240	51480	show up on the scoreboard with points, it is a pass-fail challenge. Only teams that score within
51640	56840	a time window will be eligible for podium placement and the related $50,000, $30,000,
56840	62840	and $20,000 prizes. Since there's a lot of data being displayed on our octagon scoreboard,
62840	67200	otherwise known as that thing you're looking at when it's not my face on this YouTube feed,
67200	72760	here's a quick primer on some of the elements. First, the display on the left shows a scoreboard
72760	77680	breakdown that breaks down each team's points earned per challenge, shows the total score,
77680	82580	and includes a log of recent solves and messages sent from each team to their Flatsat.
82600	86500	Note that the message contents have actually been sanitized to not give away answers,
86500	88940	but you might find some other things there instead.
89900	95640	On the right scoreboard, you'll see the time of the teams, you see the score of the teams over time.
95960	99520	Right now it's skewed a little bit to the left, but as the game progresses, it'll stretch out
99520	105500	and we'll see how they do on each of these new challenges. Finally, each team has a dedicated
105500	111120	panel with a main view and three supplementary views. Technically, we can change the supplementary
111120	117420	views, but right now the main view shows a team logo with their color, a representation of the
117420	122820	team's Flatsat, including their rotation, position over the earth, and messages sent. Note that the
122820	128060	little pew-pew you see are just for visual effect and not actually representative of actual messages
128060	133380	being sent. On the graph right now on the right, excuse me, the three graphs on the right, the top
133380	139160	graph is yaw, the middle graph is angular velocity, and the bottom graph is total messages, all done
139160	144200	over time, which makes for a nice overview of the different activity from each team's Flatsat.
144200	148900	Remember, you can vote to control which of these views you're looking at in the virtual environment
148900	154260	inside of the Stardome. That feed doesn't cut over these live updates and always shows the octagon.
154840	158540	While we wait on our teams to continue to solve these challenges they're working on,
158540	163540	now's a great time to introduce another segment we call Space Talk. If, like me, you're a hacker
163540	167880	who might know about computers but is ignorant of what goes into making code run in space,
167880	172760	there's a lot of new things to learn. Our first Space Talk episode is about how to keep track of
172760	195460	time in space. So what time is it in space? Well, that's a complicated question. For the astronauts
195460	199960	on the International Space Station, and for most orbiting satellites, they run on Coordinated
199960	206760	Universal Time, or UTC. It's not actually a time zone but rather a time standard that just so
206760	213420	happens to be the same as GMT. It's used to prevent time zone confusion and give a standard time to
213420	220280	reference. But for astronauts especially, it's just a number. On the International Space Station,
220280	225460	the sun rises and sets about every 90 minutes, so there isn't any relationship between the sun
225460	230280	and what time it is that's meaningful to the astronauts. Satellites are the same way. Time is
230280	236380	primarily used to inform them when to execute commands and perform operations. Universal time
236380	242900	is just a reference number that's easy to relate back to your local time. But that's not the only
242900	249720	time that's used for space applications. UTC is not an exact accounting of the passage of time,
249720	255280	but rather strives to stay aligned with the rotation of the Earth, because it's primarily
255280	260580	people on Earth that are using it. Earth's rotation is both irregular in the short term
260580	266160	and slowing down permanently in the long term. Earth days are getting about 1.6 milliseconds
266160	272280	longer every single day. This isn't in any way noticeable in daily life, but can be very
272280	277540	significant over time. As a result, we use a different time scale when dealing with orbital
277540	283480	motion. Orbital motion doesn't care about the Earth's rotation at all. It must be extremely
283480	289780	precise because of the massive distances involved. The most common time standards used are Julian
289780	296340	date and terrestrial time, which are both entirely independent of Earth's rotation. To give an idea
296340	303480	of just how different these time scales can be, over the last century between 1900 and 2000,
303480	310800	universal time was about 64 seconds slower than terrestrial time. It's a tiny difference to us,
310800	316400	but when you're dealing with precise predictions over millions of miles, it gets very significant.
316400	322620	And that's the key. What time it is in space isn't important so you can look at the clock on the wall
322620	328580	and know if you need to go to bed. It's important so you can know where you are and know where
328580	335080	things are. Everything in space is constantly moving, orbiting one object or another. Telling
335080	341060	where it's located is intrinsically linked to what time it is. This gets to our next question.
341120	346300	How do you tell where something is in space? As I said before, everything in space is constantly
346300	351960	moving and orbiting around something else. All this motion is primarily controlled by gravity.
351960	357280	So to know where something is right now, we use where it was at some time in the past,
357280	362420	and we predict where it is now based on the laws of gravitational motion. Now you might ask,
362420	367160	how do I tell you where it is or even where it was? On earth, I could tell you where to go based
367160	373920	on your address or some landmark, and these are useful frames of reference that we can use to
373920	379600	fully communicate where something is. In space, there are an infinite number of reference frames
379600	384920	that we can use, but we also have an added complexity. Since again, everything is moving
384920	390540	all the time, to have a frame of reference, we need to incorporate time. There are several
390540	395700	different ways of describing where things are, but we typically focus on two reference frames.
395940	401000	One, what's easiest for us to use. For example, if I want to take a photo of the moon, I would
401000	406080	want to know where the moon is in relation to where I'm going to be when I have my camera.
406080	412820	Two, what's easiest to calculate. Orbital math is hard and many times impossible, so
412820	418980	picking a reference frame that makes your calculation as easy as possible is often necessary.
418980	423700	This reference point is usually whatever has the most significant gravitational effect
423700	429500	and ignores all other motion. For satellites, we use earth. We want to know where they are relative
429500	434120	to our location on the earth. This frame of reference is called earth-centered earth fix,
434120	441820	or ECEF, as it is rotating with the earth and is fixed to it. It's the same as GPS coordinates,
441820	446780	but it's much, much easier to calculate the position of the satellite when we ignore the
446780	451360	rotation of the earth, which is a different frame of reference called earth-centered inertial,
451360	458740	or ECI. So if I saw where a satellite was in relation to me in the ECEF frame at time t0,
458740	465920	and I need to know where the satellite will be in relation to me in the ECEF frame at time t1,
465920	471820	we actually need to calculate three different steps. One, translate the coordinates I observed
471820	482200	at t0 in ECEF to ECI at t0. Two, translate the orbital motion of the satellite in ECI from t0
482200	489020	to t1, where our calculations are easier. And three, translate the coordinates I calculated at
489020	497760	t1 back to ECEF from ECI. Steps one and three both require translating between these coordinate
497760	503940	frames ECEF and ECI. So how do we do that translation? Here is where we now introduce
503940	509540	the idea of an epoch. An epoch is a point in time that we use as a reference to translate between
509540	516840	these types of frames. Specifically, we use the J2000 or Julian date 2000 epoch to translate
516840	526080	between ECEI and ECEF as we set the ECI reference frame to be the same as the ECEF at that time.
526080	531020	That way we can calculate the translation between them by calculating how much the earth has
531020	537000	rotated since Julian date 2000. This is a simplification of the constant translation
537000	542580	and calculation done throughout satellites, space technology, and astronomy. But that is
542580	547860	why time and space are both extremely important and highly dependent on really what you're looking
547860	569630	to do with them. Thanks to Jess Coffey for putting those videos together. That one was epic. Now this
569630	575550	was going to be where I signed off for this update, but as we were live, PFS actually jumped up on the
575550	581290	scoreboard yet again, solving challenge two. This means that we can now move on to exposing
581290	590010	all teams to challenge three. Challenge three. Here's what we know. With the repair complete
590010	594790	on the GNC, the satellite has stopped spinning, but we still can't communicate with the payload
594790	599910	module or operate the imager. We have to ask ourselves, what else did they damage on this
599910	604910	satellite? The challenge? Teams must restore communication with the payload module so we
604910	616590	can get it working again. This has been our last hourly update for the day. I'm looking forward to
616590	622890	seeing everyone back here at 4 p.m. Pacific, 7 p.m. Eastern for a daily recap of all that's happened so far.