The Design and Engineering of Curiosity
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Jordan E (2012) Mars Science Laboratory differential restraint: The devil is in the details. Paper presented at the 41st Aerospace Mechanisms Symposium, May 16–18, 2012, Pasadena, California, USA
JPL (2012a) Spacecraft Computer Issue Resolved. http://mars.jpl.nasa.gov/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1206. Status report dated 9 Feb 2012, accessed 7 Jan 2015
JPL (2012b) Mars-Bound NASA Craft Adjusts Path, Tests Instruments. http://mars.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1211. Status report dated 26 Mar 2012, accessed 11 Feb 2016
Karlgaard C et al (2014) Mars Science Laboratory Entry Atmospheric Data System Trajectory and Atmosphere Reconstruction. Journal of Spacecraft and Rockets 51:4, DOI: 10.2514/1.A32770
Kornfeld R et al (2014) Verification and validation of the Mars Science Laboratory/Curiosity rover entry, descent, and landing system. Journal of Spacecraft and Rockets 51:4, DOI: 10.2514/1.A32680
Little A et al (2013) The Mars Science Laboratory (MSL) Entry, Descent, and Landing Instrumentation (MEDLI): hardware performance and data reconstruction. Paper presented to the 36th AAS Guidance and Control Conference, 1–6 Feb 2013; Breckenridge, CO, USA
Manning R and Simon W (2014) Mars Rover Curiosity. Smithsonian Books, Washington, DC
Martin-Mur T et al (2012) Mars Science Laboratory Navigation Results. Paper presented at the 23rd International Symposium on Space Flight Dynamics, 29 Oct–2 Nov 2012, Pasadena, CA, USA
Martin-Mur T et al (2014) Mars Science Laboratory interplanetary navigation. Journal of Spacecraft and Rockets 51:4, DOI: 10.2514/1.A32631
McEwen A (2012) Impacts from MSL tungsten blocks and cruise stage. http://www.uahirise.org/ESP_029245_1755, image caption dated 5 Dec 2012, accessed 7 Jan 2015
Mendeck G and Craig McGrew L (2014) Entry guidance design and postflight performance for 2011 Mars Science Laboratory mission. Journal of Spacecraft and Rockets 51:4, DOI: 10.2514/1.A32737
NASA (2011a) Mars Science Laboratory Launch. Press kit dated Nov 2011
NASA (2011b) NASA Ready for November Launch of Car-Size Mars Rover. Press release dated 19 Nov 2011
NASA (2011c) NASA Mars-Bound Rover Begins Research In Space. Press release dated 13 Dec 2011
NASA (2012a) Mars Science Laboratory Landing. Press kit dated Jul 2012
NASA (2012b) First words of safe landing on Mars - Tango Delta Nominal. http://www.nasa.gov/mission_pages/msl/news/msl20120821f.html posted 21 Aug 2012, accessed 23 Feb 2016
Novak K et al (2016) Thermal response of the Mars Science Laboratory spacecraft during entry, descent, and landing. Paper presented to the 46th International Conference on Environmental Systems, 10–14 Jul 2016, Vienna, Austria
Pearlman R (2017) From space plane to sky crane: How part of a space shuttle landed a rover on Mars. http://www.planetary.org/blogs/guest-blogs/2017/0804-from-space-plane-to-sky-crane.html article dated 5 Aug 2017, accessed 27 Oct 2017.
Pollard B (2012) Radar Terminal Descent Sensor (TDS). Presentation given to the JPL Section 334 Forum, 3 Aug 2012, Pasadena, CA, USA
Schratz B et al (2014) Telecommunications performance during entry, descent, and landing of the Mars Science Laboratory. Journal of Spacecraft and Rockets 51:4, DOI: 10.2514/1.A32790
Sell S et al (2014) Powered flight design and performance summary for the Mars Science Laboratory mission. Journal of Spacecraft and Rockets 51:4, DOI: 10.2514/1.A32682
Steltzner A et al (2010) Mars Science Laboratory entry, descent, and landing system overview. Revised version of Steltzner A et al (2006) Mars Science Laboratory entry, descent, and landing system. Paper presented at the 2006 IEEE Aerospace Conference, 4–11 Mar 2006, Big Sky, Montana, USA
United Launch Alliance (2011) Atlas V MSL Mission Overview. Press kit.
Wallace M (2012) Curiosity: The Next Mars Rover. Presentation to the Royal Aeronautical Society, Applied Aerodynamics Group Conference, 17–19 Jul 2012, London, UK
Way D et al (2013) Assessment of the Mars Science Laboratory entry, descent, and landing simulation. Paper presented at 23rd AAS/AIAA Space Flight Mechanics Meeting, 10–14 Feb 2013, Kauai, Hawaii, USA
Footnotes
1Details of the launch and cruise events throughout this section are from Abilleira (2013)
2Abilleira (2013)
3Allen Chen, personal communication, email dated July 1, 2016, correcting numbers published before launch
4Bhandari et al (2011)
5Abilleira (2013)
6JPL (2012a)
7The story about how the navigators pulled off the first Trajectory Correction Maneuver was shared with me in an email by Rob Manning on January 8, 2015, and corrects timeline errors he made in his book, Mars Rover Curiosity
8NASA (2011c)
9JPL (2012b)
10Martin-Mur et al (2012)
11Martin-Mur et al (2014)
12Martin-Mur et al (2014)
13Table data are from Abilleira, 2013. For a detailed accounting of the nature and reasons of all the cruise turns and calibrations, read Martin-Mur et al (2014)
14Chang (2012)
15Guy Webster, personal communication, email dated May 17, 2017
16Chen et al (2014)
17Martin-Mur et al (2014)
18Abilleira (2013)
19The details of EDL telecommunications in this section are based on Schratz et al (2014)
20Schratz et al (2014)
21Edquist K et al (2009)
22Allen Chen, personal communication, email dated July 1, 2016, correcting numbers published before the launch
23Little et al (2013)
24McEwen A (2012)
25Abilleira and Shidner (2012)
26Way et al (2013)
27Allen Chen, personal communication, email dated February 24, 2016
28Martin-Mur et al (2014)
29Mendeck and Craig McGrew (2014)
30Bose et al (2013)
31Little et al (2013)
32Mendeck and Craig McGrew (2014)
33Mendeck and Craig McGrew (2014)
34Martin-Mur et al (2014)
35Way et al (2013)
36Cruz et al (2014)
37Baker et al (2014)
38Way et al (2013)
39Cruz et al (2014)
40Hoffman et al (2007)
41Pearlman (2017)
42Cruz et al (2014)
43Karlgaard et al (2014)
44Chen and Pollard (2014)
45Steltzner et al (2010)
46Christian Schaller, personal communication, email dated February 17, 2016
47Karlgaard et al (2014)
48Steltzner et al (2010)
49Way et al (2013)
50Sell et al (2014)
51Jordan (2012)
52Gallon (2012)
53Sell et al (2014)
54Jordan (2012)
55Way et al (2013)
56Manning and Simon (2014)
57Way et al (2013)
58Baker et al (2014)
59This was explained at the August 6, 2012 post-landing press briefing
60Baker et al (2014)
61NASA (2012b)
62Way et al (2013)
63John Grotzinger told me this after the end of the press briefing on August 6, 2012
© Springer International Publishing AG, part of Springer Nature 2018
Emily LakdawallaThe Design and Engineering of CuriositySpringer Praxis Bookshttps://doi.org/10.1007/978-3-319-68146-7_3
3. Mars Operations
Emily Lakdawalla1
(1)The Planetary Society, Pasadena, CA, USA
3.1 INTRODUCTION
Operating a lander is quite different from operating an orbiter or flyby craft. Navigators steer orbiters’ paths long in advance, so scientists can plan observations months ahead. Rovers don’t have the luxury of predictability. Each day’s activities can’t be planned until controller
s back on Earth have received data that tell them the condition and state of the spacecraft, and the lay of the landscape surrounding it. A team can do strategic planning – make a list of top-level science goals – in advance, but to accomplish the strategic plan, the team has to develop a new tactical plan each Martian sol. To make things more complicated, Martian sols are not quite the same length as Earth days.
NASA performed tactical planning for the first time on another world with the Surveyor lunar landers, and later with the Viking and Pathfinder landers, but tactical planning was elevated to an art form with the Mars Exploration Rovers. Over a decade of mission operations, the Spirit and Opportunity teams perfected a way of planning the daily operations of a rover on another world, beginning by working on “Mars time,” then switching to an Earth time schedule.1 Curiosity followed in their tracks, but the complexity of its instrument package required some changes to the Spirit and Opportunity way of doing things.
3.2 MARS’ CALENDAR
3.2.1 Mars sols and seasons
Mars missions are bound to the same kinds of celestial cycles that dictate Earth’s 24-hour days, 365-day years, and four seasons. When it comes to days and seasons, Mars has some coincidental similarities to Earth. Mars’ solar days are just 3% longer than Earth days, being 24 hours 39 minutes 35.244 seconds long, on average. To differentiate Earth days from Mars days, one Mars solar day is called a “sol”, a term coined during the Viking missions.2 Because of the similarity in day length, Mars landed mission time can be run on a 24-hour clock, with hours split into 60 minutes of 60 seconds each, just like on Earth. Mars seconds are 1.0275 Earth seconds long.
Mars’ axial tilt is also similar to Earth’s at 25.2°, resulting in Earth-like seasons of spring, summer, fall, and winter. Curiosity landed 4.6° south of the equator, so the southern hemisphere seasons are relevant. Scientists measure the seasons on Mars using solar longitude, abbreviated Ls (pronounced “ell sub ess”). Ls is 0° at the southern autumnal equinox (beginning of northern spring), 90° at southern winter solstice, 180° at southern vernal equinox, and 270° at summer solstice.
Mars’ years last 687.9726 Earth days or 668.5921 Mars sols. Because Mars’ orbit is eccentric, Mars’ distance to the Sun varies over the course of a year: it is 206.62 million kilometers from the Sun at perihelion, but 249.23 million kilometers away at aphelion. The difference in distance means the Sun is 45% brighter at perihelion than at aphelion. Aphelion happens at Ls=70°, just before southern winter solstice (Figure 3.1).
Figure 3.1. Geometry of Mars’ orbit. See text for discussion.
Planets move faster when close to perihelion than they do when near to aphelion, and the difference is stark for Mars. Winters in Mars’ southern hemisphere, which begin near aphelion, are long and cold under a fainter, distant Sun. Summers are short and hot, with a big Sun overhead. Autumn is the longest season in the southern hemisphere, at 194 sols; winter has 178 sols; spring has 142 sols; and summer has 154 sols.
To discuss the passage of years, Mars atmospheric scientists have settled upon a convention first defined by Bruce Cantor, Philip James, and Wendy Calvin in a 2010 paper. Mars years begin at Ls=0°, and the beginning of Mars year 1 on April 11, 1955. The choice of year 1 is, of course, arbitrary, but it is about one Mars year before the Space Age began with the launch of Sputnik in 1957.3 Curiosity landed at Ls=151° of Mars year 31, after the coldest part of winter had passed, headed into spring. Years and seasons relevant to the Curiosity mission are listed in Table 3.1.Table 3.1. Mars seasons relevant to the Curiosity mission. Data from Cantor et al ( 2010 ).
Mars year
Northern spring/southern autumn equinox (Ls = 0°)
Northern summer / southern winter solstice (Ls = 90°)
Northern autumn / southern spring equinox (Ls = 180°)
Northern winter/southern summer solstice (Ls = 270°)
31
Sep 13 2011
Mar 30 2012
Sep 29 2012 / sol 53
Feb 23 2013 / sol 196
32
Jul 31 2013 / sol 350
Feb 15 2014 / sol 543
Aug 17 2014 / sol 722
Jan 11 2015 / sol 865
33
Jun 18 2015 / sol 1019
Jan 03 2016 / sol 1212
Jul 04 2016 / sol 1390
Nov 28 2016 / sol 1533
34
May 05 2017 / sol 1687
Nov 20 2017 / sol 2059
May 22 2018
Oct 16 2018
35
Mar 23 2019
Oct 08 2019
Apr 08 2020
Sep 02 2020
36
Feb 07 2021
Aug 25 2021
Feb 24 2022
Jul 21 2022
37
Dec 26 2022
Jul 12 2023
Jan 12 2024
Jun 07 2024
38
Nov 12 2024
May 29 2025
Nov 29 2025
Apr 25 2026
39
Sep 30 2026
Apr 16 2027
Oct 17 2027
Mar 12 2028
40
Aug 17 2028
Mar 03 2029
Sep 03 2029
Jan 28 2030
3.2.2 Mars solar time
Curiosity may be nuclear-powered but needs sunlight to take photos and warm its motors, so solar time rules its activities. Keeping track of sunrise and sunset times has to take into account Mars’ orbital eccentricity, which makes the solar day length vary slightly over the course of the year. To simplify timekeeping, there is a defined convention of local mean solar time (LMST), counting time in evenly advancing increments. It approximates local true solar time (LTST). Mean and true solar time are identical close to aphelion and perihelion, at Ls=57.7° and 258.0°. They are most dissimilar at Ls=187.9°, when mean solar time runs behind true solar time by 39.9 minutes, and at Ls=329.1°, when mean solar time runs ahead of true solar time by 51.1 minutes (Figure 3.2).4 Curiosity (like all landed Mars missions) operates according to a mean solar time clock so that every sol is of the same length, but tracking local true solar time is very important for thermal control and camera systems.5 In this book I’ll generally refer to the two interchangeably as “local time,” differentiating between local mean and local true solar time only if the situation requires it.
Figure 3.2. Difference between mean and true solar time as a function of solar longitude. Emily Lakdawalla after Allison ( 1997 )
3.2.3 Rover timekeeping
One way the mission measures time is with the spacecraft clock, which counts time in seconds. Landing happened at a spacecraft clock time of 397502503. The mission calendar is reckoned in sols, counting up from landing day on sol 0.
The rover motion counter (RMC) is another way of ordering rover activities, including science, in time. The rover motion counter comprises 10 integer indices, keeping track of when various rover motors have operated. In order, the 10 indices are site, drive, pose, arm, CHIMRA, drill, mast, high-gain antenna, brush, and inlet covers. The site index increments every time the rover updates its knowledge of its geographic location, so has been counting up since the beginning of the mission. Curiosity increments the site index when it updates its knowledge of its orientation by sighting the Sun with the Navcam (see section 6.5.1); incrementing the site index sets all other indices to 0. The drive index increments every time the rover rolls or steers its wheels. Incrementing the drive index sets all other indices except site to 0. All science data with the same site/drive index is from the same geographic location. The rest of the indices increment whenever the relevant motor is operated, and help to place activities in order at a specific site/drive location.