[00:01.240 --> 00:04.260]  Let's take a look at solving the on-orbit challenge.
[00:04.360 --> 00:06.760]  First, some terms you'll want to know.
[00:07.020 --> 00:09.240]  Two-line element set, or TLE.
[00:09.400 --> 00:12.900]  A data format containing information about an object's position and velocity
[00:12.900 --> 00:15.000]  at a specific point in time.
[00:15.000 --> 00:18.240]  It is used to calculate where a satellite will be at some point in the future,
[00:18.240 --> 00:21.140]  with increasing uncertainty the further out in time.
[00:21.140 --> 00:22.760]  Window of opportunity.
[00:22.940 --> 00:27.640]  The period of time during which the satellite can be positioned to complete the desired goal.
[00:28.120 --> 00:29.040]  Vector.
[00:29.040 --> 00:32.460]  A line indicating a specific direction and magnitude.
[00:32.500 --> 00:36.980]  A satellite will have assigned X, Y, and Z vectors associated with the body of the vehicle
[00:36.980 --> 00:39.580]  that can be used in a coordinate system.
[00:39.640 --> 00:43.300]  Camera boresight, camera mounting position, and camera body vector
[00:43.300 --> 00:46.780]  all describe the satellite camera and where it's pointed.
[00:46.940 --> 00:47.860]  Quaternion.
[00:47.860 --> 00:51.520]  A number system that is handy for calculating 3D rotations.
[00:52.060 --> 00:54.060]  Got it? Here we go.
[00:54.060 --> 00:56.600]  The first step in solving the on-orbit challenge.
[00:56.640 --> 00:58.320]  Identify the key data.
[00:58.320 --> 01:02.400]  The TLE, camera mounting position, target, and window of opportunity
[01:02.400 --> 01:06.520]  are all supplied in the challenge description or the on-orbit handbook.
[01:06.620 --> 01:09.980]  The data is used to calculate the orbit of both the satellite and the moon
[01:09.980 --> 01:11.740]  toward the window of opportunity.
[01:11.740 --> 01:15.740]  And don't forget to grab the camera body vector, which will be needed later.
[01:15.960 --> 01:17.100]  The second step.
[01:17.100 --> 01:21.480]  Calculate the time of image by defining the relationship between these key vectors.
[01:21.780 --> 01:24.540]  1. Determine the satellite to moon vector,
[01:24.540 --> 01:27.140]  which points directly from the satellite towards the moon.
[01:27.140 --> 01:29.100]  2. Determine the nadir vector,
[01:29.100 --> 01:32.540]  which points directly from the satellite towards the center of the earth.
[01:32.540 --> 01:37.340]  3. Determine the angle between 1. The satellite to moon vector and the nadir vector
[01:37.340 --> 01:42.560]  and 2. The angle between the satellite negative z vector and the camera body vector.
[01:42.720 --> 01:45.660]  The instance when the difference between the two angles is minimized
[01:45.660 --> 01:49.120]  gives us the time of image, the moment along its orbit when the
[01:49.120 --> 01:53.240]  satellite will be in position to take our all-important moon shot.
[01:53.920 --> 01:55.560]  The third step.
[01:55.560 --> 01:59.320]  Calculate the attitude or the position within its orbit that the satellite must
[01:59.320 --> 02:05.200]  take for the camera to capture the image. This is accomplished by lots of math.
[02:05.540 --> 02:11.040]  Specifically, something called a direction cosine matrix, DCM, or rotation matrix.
[02:11.040 --> 02:15.700]  The DCM calculates a satellite attitude that points 1. The camera boresight to the moon
[02:15.700 --> 02:19.780]  and 2. The satellite's negative z vector to earth center,
[02:19.780 --> 02:22.780]  which is the attitude needed to accomplish the goal.
[02:23.500 --> 02:28.640]  The DCM supplies us with a specific quaternion which, when uploaded and applied to the satellite's
[02:28.640 --> 02:34.840]  attitude determination and control system, ADCS, moves the satellite into the desired position.
[02:35.220 --> 02:40.640]  On to the final step. Apply all that information and get the image we're after.
[02:41.340 --> 02:45.740]  We take the time of image and back out the commands around it, giving the satellite enough
[02:45.740 --> 02:50.620]  time to apply the quaternion and be in position when it arrives at the window of opportunity.
[02:50.620 --> 02:57.020]  The proper order of commands would be as follows. Turn on the ADCS, slew to the commanded quaternion,
[02:57.020 --> 03:03.880]  turn the camera on, set the exposure time, capture the image, and finally, turn the camera off.
[03:04.080 --> 03:09.240]  That's it. Challenge accomplished. But what does all of this have to do with
[03:09.240 --> 03:15.080]  hacking and keeping our satellites secure? The on-orbit challenge was completed with full trust.
[03:15.080 --> 03:19.960]  Our satellites rely on data and sensors from multiple sources in order to complete an objective.
[03:19.960 --> 03:24.440]  The TLE that was provided relied on data from the satellite and ground stations. Authenticated
[03:24.440 --> 03:29.660]  communications were required to upload the proper command sequence. Trusted execution was required
[03:29.660 --> 03:34.900]  to process sensor and actuator data to close control loops. Secure on-board communications
[03:34.900 --> 03:40.340]  were required to carry out operations in orbit. We need security-focused people to help with these
[03:40.340 --> 03:45.260]  problems because just as much as it takes a team of people to strap explosives to a computer to
[03:45.260 --> 03:50.160]  satellite into orbit, it takes a team of people from both space and security communities
[03:50.160 --> 03:54.660]  to ensure that space remains a viable, usable resource.