WEBVTT 00:11.540 --> 00:17.080 Welcome back to the competition formerly known as Space Security Challenge 2020, now HackASAT. 00:17.100 --> 00:19.100 Well, it's actually still known by Moth. 00:19.100 --> 00:22.840 I just wanted to change the intro because they're going to get pretty repetitive. 00:22.940 --> 00:24.860 I'm your host, Jordan Wines. 00:25.040 --> 00:30.280 The game has been a little bit slower this hour, but that makes sense because teams are starting to get into the harder challenges. 00:30.380 --> 00:34.100 As a reminder, teams are currently working on two separate challenges. 00:34.100 --> 00:45.100 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. 00:45.180 --> 00:50.240 While that challenge won't show up on the scoreboard with points, it is a pass-fail challenge. 00:50.240 --> 00:58.740 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. 00:59.160 --> 01:09.660 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. 01:10.020 --> 01:22.580 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. 01:22.600 --> 01:28.940 Note that the message contents have actually been sanitized to not give away answers, but you might find some other things there instead. 01:29.900 --> 01:35.640 On the right scoreboard, you'll see the time of the teams, you see the score of the teams over time. 01:35.960 --> 01:42.940 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. 01:43.280 --> 01:49.280 Finally, each team has a dedicated panel with a main view and three supplementary views. 01:49.520 --> 02:02.340 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. 02:02.360 --> 02:09.100 Note that the little pew-pew you see are just for visual effect and not actually representative of actual messages being sent. 02:09.100 --> 02:24.200 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. 02:24.200 --> 02:30.460 Remember, you can vote to control which of these views you're looking at in the virtual environment inside of the Stardome. 02:30.500 --> 02:34.260 That feed doesn't cut over these live updates and always shows the octagon. 02:34.840 --> 02:42.200 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. 02:42.200 --> 02:49.800 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. 02:49.900 --> 02:54.600 Our first Space Talk episode is about how to keep track of time in space. 03:08.840 --> 03:11.640 So what time is it in space? 03:11.640 --> 03:14.500 Well, that's a complicated question. 03:14.820 --> 03:22.560 For the astronauts on the International Space Station, and for most orbiting satellites, they run on Coordinated Universal Time, or UTC. 03:22.560 --> 03:29.280 It's not actually a time zone but rather a time standard that just so happens to be the same as GMT. 03:29.280 --> 03:34.400 It's used to prevent time zone confusion and give a standard time to reference. 03:34.400 --> 03:38.320 But for astronauts especially, it's just a number. 03:38.760 --> 03:48.400 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. 03:48.440 --> 03:49.980 Satellites are the same way. 03:49.980 --> 03:55.160 Time is primarily used to inform them when to execute commands and perform operations. 03:55.580 --> 04:01.400 Universal time is just a reference number that's easy to relate back to your local time. 04:01.400 --> 04:05.500 But that's not the only time that's used for space applications. 04:05.980 --> 04:17.780 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. 04:18.000 --> 04:23.560 Earth's rotation is both irregular in the short term and slowing down permanently in the long term. 04:23.560 --> 04:28.320 Earth days are getting about 1.6 milliseconds longer every single day. 04:28.320 --> 04:34.000 This isn't in any way noticeable in daily life, but can be very significant over time. 04:34.000 --> 04:38.560 As a result, we use a different time scale when dealing with orbital motion. 04:38.740 --> 04:42.060 Orbital motion doesn't care about the Earth's rotation at all. 04:42.060 --> 04:47.080 It must be extremely precise because of the massive distances involved. 04:47.080 --> 04:55.640 The most common time standards used are Julian date and terrestrial time, which are both entirely independent of Earth's rotation. 04:55.720 --> 05:08.400 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. 05:08.420 --> 05:16.400 It's a tiny difference to us, but when you're dealing with precise predictions over millions of miles, it gets very significant. 05:16.400 --> 05:17.480 And that's the key. 05:17.480 --> 05:24.940 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. 05:24.940 --> 05:30.000 It's important so you can know where you are and know where things are. 05:30.000 --> 05:34.740 Everything in space is constantly moving, orbiting one object or another. 05:34.820 --> 05:39.060 Telling where it's located is intrinsically linked to what time it is. 05:39.060 --> 05:41.060 This gets to our next question. 05:41.120 --> 05:44.060 How do you tell where something is in space? 05:44.060 --> 05:49.180 As I said before, everything in space is constantly moving and orbiting around something else. 05:49.180 --> 05:51.960 All this motion is primarily controlled by gravity. 05:51.960 --> 06:01.720 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. 06:01.720 --> 06:05.540 Now you might ask, how do I tell you where it is or even where it was? 06:05.540 --> 06:16.460 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. 06:16.460 --> 06:23.120 In space, there are an infinite number of reference frames that we can use, but we also have an added complexity. 06:23.120 --> 06:29.700 Since again, everything is moving all the time, to have a frame of reference, we need to incorporate time. 06:30.020 --> 06:35.700 There are several different ways of describing where things are, but we typically focus on two reference frames. 06:35.940 --> 06:38.680 One, what's easiest for us to use. 06:38.680 --> 06:46.080 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. 06:46.080 --> 06:49.280 Two, what's easiest to calculate. 06:49.280 --> 06:58.980 Orbital math is hard and many times impossible, so picking a reference frame that makes your calculation as easy as possible is often necessary. 06:58.980 --> 07:06.220 This reference point is usually whatever has the most significant gravitational effect and ignores all other motion. 07:06.220 --> 07:07.940 For satellites, we use earth. 07:07.940 --> 07:11.160 We want to know where they are relative to our location on the earth. 07:11.160 --> 07:19.560 This frame of reference is called earth-centered earth fix, or ECEF, as it is rotating with the earth and is fixed to it. 07:19.560 --> 07:32.580 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. 07:32.580 --> 07:49.500 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. 07:49.500 --> 07:57.000 One, translate the coordinates I observed at t0 in ECEF to ECI at t0. 07:57.000 --> 08:05.920 Two, translate the orbital motion of the satellite in ECI from t0 to t1, where our calculations are easier. 08:05.920 --> 08:13.780 And three, translate the coordinates I calculated at t1 back to ECEF from ECI. 08:13.780 --> 08:20.620 Steps one and three both require translating between these coordinate frames ECEF and ECI. 08:20.620 --> 08:22.740 So how do we do that translation? 08:22.740 --> 08:25.440 Here is where we now introduce the idea of an epoch. 08:25.440 --> 08:30.960 An epoch is a point in time that we use as a reference to translate between these types of frames. 08:30.960 --> 08:46.080 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. 08:46.080 --> 08:54.460 That way we can calculate the translation between them by calculating how much the earth has rotated since Julian date 2000. 08:54.460 --> 09:02.040 This is a simplification of the constant translation and calculation done throughout satellites, space technology, and astronomy. 09:02.040 --> 09:09.260 But that is why time and space are both extremely important and highly dependent on really what you're looking to do with them. 09:23.770 --> 09:26.510 Thanks to Jess Coffey for putting those videos together. 09:26.510 --> 09:28.530 That one was epic. 09:28.930 --> 09:38.770 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. 09:38.770 --> 09:43.610 This means that we can now move on to exposing all teams to challenge three. 09:44.610 --> 09:46.250 Challenge three. 09:47.370 --> 09:48.870 Here's what we know. 09:48.870 --> 09:56.710 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. 09:56.710 --> 10:00.950 We have to ask ourselves, what else did they damage on this satellite? 10:00.970 --> 10:02.030 The challenge? 10:02.030 --> 10:06.430 Teams must restore communication with the payload module so we can get it working again. 10:13.150 --> 10:15.710 This has been our last hourly update for the day. 10:15.710 --> 10:18.370 I'm looking forward to seeing everyone back here at 4 p.m. 10:18.370 --> 10:19.590 Pacific, 7 p.m. 10:19.590 --> 10:22.890 Eastern for a daily recap of all that's happened so far.