1
00:00:07,600 --> 00:00:12,480
So, in my job as the spacecraft science phase 
lead, I get to work hand-in-hand with the  

2
00:00:12,480 --> 00:00:17,440
scientists and the navigation team to plan 
out this mission and how OSIRIS-REx is going  

3
00:00:17,440 --> 00:00:22,880
to execute this. For me personally this is an 
ideal combination. I've always loved deep space  

4
00:00:22,880 --> 00:00:28,320
exploration and the science behind it, so I get to 
work one-on-one with the science teams to identify  

5
00:00:28,320 --> 00:00:31,920
really what their science goal is and translate 
that for the spacecraft team to something that  

6
00:00:31,920 --> 00:00:37,252
we can actually execute, piece by piece, as 
the spacecraft goes through its commanding.

7
00:00:46,400 --> 00:00:50,960
So, one of the challenges that OSIRIS-REx has 
been facing is the microgravity environment that  

8
00:00:50,960 --> 00:00:56,320
we are in when we orbit Bennu. We don't have the 
strong pull of gravity below us, so instead, the  

9
00:00:56,320 --> 00:01:00,560
non-gravitational forces in the spacecraft affect 
our trajectory a lot more than what we're used to.

10
00:01:00,560 --> 00:01:05,120
So over the course of a few weeks, we could 
end up on a number of different trajectories,  

11
00:01:05,120 --> 00:01:10,400
and that means our uncertainty in planning and 
our responsibility to keep the spacecraft safe  

12
00:01:10,400 --> 00:01:15,200
is very challenging. So we have to constantly 
update our pointing on board the spacecraft,  

13
00:01:15,200 --> 00:01:18,080
both for maneuvers and for 
science pointing purposes.  

14
00:01:18,080 --> 00:01:22,240
And we have to constantly reanalyze the 
sun angles on the spacecraft to make sure  

15
00:01:22,240 --> 00:01:26,320
that the power and thermal and telecom attitudes 
are safe for the spacecraft to navigate.

16
00:01:31,680 --> 00:01:36,000
So, when we're orbiting around Bennu, the 
force of gravity on the spacecraft is about  

17
00:01:36,000 --> 00:01:39,600
one millionth what the force of 
gravity at Mars is for our spacecraft,  

18
00:01:39,600 --> 00:01:43,200
so that's a significant change in 
the forces that spacecraft feels,  

19
00:01:43,200 --> 00:01:48,080
and it means that the non-gravitational forces, 
such as solar radiation pressure, are within an  

20
00:01:48,080 --> 00:01:52,848
order of magnitude of gravity, which is a very 
new environment for us to be operating in.

21
00:01:58,160 --> 00:02:03,120
So, OSIRIS-REx comes with an instrument suite that 
was uniquely designed to observe the asteroid,  

22
00:02:03,120 --> 00:02:08,080
but the spacecraft itself was also designed 
to observe this asteroid. Our science mission  

23
00:02:08,080 --> 00:02:12,640
requires us to observe and map all over the 
surface of the asteroid under a number of  

24
00:02:12,640 --> 00:02:17,280
different lighting conditions. To support that, 
all of our subsystems have been tuned for this  

25
00:02:17,280 --> 00:02:22,640
purpose. So our solar arrays are gimballed so 
we can continue to keep a power positive margin  

26
00:02:22,640 --> 00:02:27,040
as we look at different sun angles and different 
sites around the surface of the asteroid. Our  

27
00:02:27,040 --> 00:02:31,760
thruster suites, we have very low thrust engines 
that allow us to do very tiny, precision pointing  

28
00:02:31,760 --> 00:02:37,360
maneuvers around the asteroid. On board, our 
software, for instance, has a targeting software.  

29
00:02:37,360 --> 00:02:41,360
It allows us to load up a list of targets from 
the science teams and tell the spacecraft to  

30
00:02:41,360 --> 00:02:46,480
execute them autonomously as it maps out the 
surface of Bennu for us, and additionally, we  

31
00:02:46,480 --> 00:02:50,640
have an engineering camera which we use to support 
the optical navigation that this mission needs.

32
00:02:54,880 --> 00:02:59,280
So, before launch we expected that the surface of 
Bennu would be covered in a fine-grained material  

33
00:02:59,280 --> 00:03:04,960
much like the lunar regolith on the surface of the 
Moon. This was supported by the observations that  

34
00:03:04,960 --> 00:03:09,600
the science teams had done of Bennu before 
launch. They used ground-based astronomy,  

35
00:03:09,600 --> 00:03:15,520
radio astronomy, and infrared imaging to deduce 
the thermal inertia of the surface material on  

36
00:03:15,520 --> 00:03:20,640
Bennu. When we got to Bennu, we found, to our 
surprise, that instead it's covered in a lot of  

37
00:03:20,640 --> 00:03:25,200
rocky material and it's a much rougher surface 
than we were expecting. We've had to adapt our  

38
00:03:25,200 --> 00:03:31,840
science plan and our sample acquisition plan 
to this new rocky surface of Bennu instead.

39
00:03:34,720 --> 00:03:40,160
Before launch, we had developed two methods to 
guide ourselves in for TAG. We had a primary  

40
00:03:40,160 --> 00:03:45,760
method which was to use our lidar to do a ranging 
acquisition. As we approach the TAG site and  

41
00:03:45,760 --> 00:03:49,760
guide ourselves in, that was our primary method 
that we did the majority of our development on.  

42
00:03:50,320 --> 00:03:54,640
We developed a backup method using natural 
feature tracking which is an optical navigation  

43
00:03:54,640 --> 00:04:00,320
used on board autonomously to image the site, 
compare it to a catalog, and guide ourselves in.  

44
00:04:00,320 --> 00:04:06,176
When we got to Bennu, the rocky surface of 
Bennu really changed our entire approach to TAG.  

45
00:04:06,320 --> 00:04:12,400
Originally, we had expected to be able to find a 
25 meter radius site that could be safe to TAG in,  

46
00:04:12,400 --> 00:04:16,880
that would be full of this fine-grained material, 
and wouldn't have uneven surfaces that could  

47
00:04:16,880 --> 00:04:22,560
be dangerous for the spacecraft. Unfortunately, 
Bennu did not know about our expectations for it,  

48
00:04:22,560 --> 00:04:27,840
and when we got there, we found that there weren't 
sites large enough to meet that need. Without that  

49
00:04:27,840 --> 00:04:33,120
large site, the lidar approach could no longer 
support the increased performance that we needed,  

50
00:04:33,120 --> 00:04:36,800
and the natural feature tracking 
with its higher precision targeting  

51
00:04:36,800 --> 00:04:42,080
could get us to a site that was smaller and could 
fit within the smaller smooth surfaces of Bennu.

52
00:04:49,120 --> 00:04:52,080
So, we've just completed our Match 
Point rehearsal, and we got to see  

53
00:04:52,080 --> 00:04:57,920
a second demonstration of how well NFT 
has been used to predict our TAG profile.  

54
00:04:57,920 --> 00:05:01,680
And in our last rehearsal, we 
saw NFT come in within two meters  

55
00:05:01,680 --> 00:05:05,120
of the TAG site which is really impressive 
when you consider that our original design  

56
00:05:05,120 --> 00:05:10,880
was to come within 25 meters of a TAG site. So 
NFT's onboard performance and the tuning that  

57
00:05:10,880 --> 00:05:16,160
our ground team has done to perfect NFT over 
the last few years has allowed us to get an  

58
00:05:16,160 --> 00:05:20,160
order of magnitude better performance out of the 
spacecraft than it was designed for, and that's  

59
00:05:20,160 --> 00:05:24,320
what we need to be able to TAG successfully 
on this small TAG site that Bennu has for us.

60
00:05:29,520 --> 00:05:34,400
For me the most exciting part about OSIRIS-REx has 
been the same thing that causes the challenges:  

61
00:05:34,400 --> 00:05:39,280
it's the dynamic nature of this mission and how 
much we are dependent on what we learn from the  

62
00:05:39,280 --> 00:05:44,320
asteroid. Every few weeks our trajectory has to 
change, and we're having to redesign the mission  

63
00:05:44,320 --> 00:05:49,265
as we fly it which gives us a whole new challenge 
for mission operations we haven't had before.  

64
00:05:49,360 --> 00:05:52,960
Traditionally, mission operations, from 
a spacecraft engineer point of view,  

65
00:05:52,960 --> 00:05:57,440
we operate the spacecraft, and we don't always 
see the results of data we're taking for a long  

66
00:05:57,440 --> 00:06:02,000
time. On Bennu the science observations 
and the results we're getting out of that,  

67
00:06:02,000 --> 00:06:07,040
feed right back into the spacecraft trajectory 
and our overall proximity operations phase,  

68
00:06:07,040 --> 00:06:11,040
so we get to see first-hand what we're 
learning about this asteroid with the  

69
00:06:11,040 --> 00:06:16,089
science teams, which has been a really rewarding 
experience for our team and for me personally.

70
00:06:20,467 --> 00:06:39,087
[Room Tone]