1. ASTR 330: The Solar System Announcements Dr Conor Nixon Fall 2006 Homework #6 due Tuesday, December 12th. Extra-credit papers will also be returned on Tuesday. This is the last regular class: Tuesday’s class will be a fun (!) team working game. This lecture will summarize some aspects of spacecraft mission which will be useful on Tuesday! On-line evaluation: https://www.courses.umd.edu/online_evaluation/

2. ASTR 330: The Solar System Space Mission Game! Dr Conor Nixon Fall 2006 Tuesdays class will take the form of a team working game. The purpose is to emulate the process which occurs in NASA, of proposing, promoting and finally selecting a space mission to fund and develop, from competing proposals. The Space Mission Game will build on Homework #6, so make sure you have completed it ahead of time! You may also want to bring some extra copies of your homework with you to distribute to team members.

3. ASTR 330: The Solar System Space Mission Game! Dr Conor Nixon Fall 2006 The class will be divided into groups of 6-7, in teams. Each team will be required to: 1.Select, from amongst your homework #6 assignments, one mission plan to present to the class. You may meld elements from several proposals into a new proposal. 2.Prepare a presentation to the class. At least two team members must present. Presentations should take about 3 minutes or less.

4. ASTR 330: The Solar System Presentations Dr Conor Nixon Fall 2006 The presentation will take the following form: 1.TITLE - giving mission name, logo, graphic, team member names. 2.SCIENCE OBJECTIVES - list no more than three principal science objectives. Say why each is important. 3.TECHNICAL PLAN - brief description of mission, and spacecraft especially instruments (max 5). Sketch. 4.SUMMARY - convince the judging panel. Presentation materials (pens, transparencies) will be provided. You will have about 40 minutes to prepare.

5. ASTR 330: The Solar System Judging and Scoring Dr Conor Nixon Fall 2006 One member from each team will volunteer to join a judging panel at the start of the class. The judging panel will devise a scoring rubric and then assess each proposal in turn. At the end, they must select one mission to fund! All students who participate will receive 10 extra credit course points. The team which receives the highest score will also receive 5 bonus extra credit course points.

6. ASTR 330: The Solar System Exams Dr Conor Nixon Fall 2006 Final exam: Tuesday December 19 th, 1:30-3:30 pm. Room CSS 2428. Final exam (120 mins): is 30% of the total course grade. Will examine all material from the whole course. The final exam will include numerical problems as well as essays. Exams will cover material from BOTH lectures AND textbook. The exam will consist of the same sections as before. Short Answer Questions True/False Statements Longer, structured answer questions.

7. ASTR 330: The Solar System Exam conduct Dr Conor Nixon Fall 2006 Closed-book, no notes or textbooks allowed. Bring your own pens and pencils and ruler. Don’t use correction fluid. No talking or other communicating between students once the papers are distributed until they are collected. Cheating will be not be tolerated. If you are seen/heard to be cheating you may be asked to leave the exam room, and the case immediately referred to the Head of Classes in the Astronomy Department. You will lose all credit for the exam and your case may be referred to the University level.

8. ASTR 330: The Solar System Example short answer question Dr Conor Nixon Fall 2006 1.Write a brief definition of the following terms and concepts, and give an example from the course: a)Greenhouse effect. b)Differentiation. c)Doppler effect. d)Ejecta blanket. e)Retrograde orbit.

9. ASTR 330: The Solar System Example True/False Question Dr Conor Nixon Fall 2006 Life in the Solar System. Circle the letter for each correct answer, cross out the letter for each incorrect answer. Then, for the incorrect answers, cross out part of the statement which is incorrect and add replacement text to make the sentence a true, positive statement. A) The two main characteristics of a living organism are metabolism and reproduction. B) The last common ancestor (LCA) is the hypothesized primate which gave rise to both chimps and humans. C) Amino acids have recently been found in space which is evidence of life.

10. ASTR 330: The Solar System True/False continued Dr Conor Nixon Fall 2006 D) Water ice has been found in the polar caps of Mars. Also, liquid water once existed on the surface of Mars, where we believe that conditions may once have been right for life to arise. E) Massive impacts were a major problem for life on Earth in the past, possibly responsible for mass extinctions (such as the dinosaurs). However, at the present day we have nothing to fear from them.

11. ASTR 330: The Solar System Example Structured Question Dr Conor Nixon Fall 2006 All four of the outer gas giant planets have ring systems. i.Describe the A, B and C rings of Saturn. Say which is the most and least bright, and what the rings are made of. ii.The F-ring is a strange narrow ring discovered by the Voyager spacecraft. Why does it not spread out and disappear? Are there similarities between this ring and the rings of Uranus and Neptune? Explain. iii.The rings of Uranus and Neptune are probably composed of a different material than most of the Saturn ring particles. Say what the differences are, and theories we have to account for this difference.

12. ASTR 330: The Solar System Lecture 28: Spacecraft Exploration of the Solar System Dr Conor Nixon Fall 2006 Picture credit: NASA/JPL

13. ASTR 330: The Solar System Spacecraft Dr Conor Nixon Fall 2006 No discussion of the planetary system would be complete without examining the technology which supplied most of our information about the planets: robotic spacecraft. Until the 20th century, planetary study was confined to telescope astronomy: a ‘hands-off’ way of exploration which limited us to recording what the skies wanted to show us. As an example, consider the far-side of the Moon. 45% of the Moon was unseen until the first spacecraft was sent there (Luna 3, 1959). With the advent of large liquid-fueled rockets combined with electronic circuits, sending probes outside the Earth’s orbit finally became possible. Unmanned craft came first, followed soon after by manned spaceships. However, so far, humans have only reached the Moon, not yet venturing beyond the Earth’s gravitational pull.

14. ASTR 330: The Solar System Types of Spacecraft Missions Dr Conor Nixon Fall 2006 Spacecraft missions broadly fall into one of the following categories: 1.Space Telescopes 2.Fly-by missions 3.Orbiter missions 4.Atmospheric probes (not designed to land). 5.Hard and soft landers 6.Rovers. 7.Hybrid/composite missions. We will discuss each type in turn, except #1, which are more similar to the Earth-based telescopes discussed in Lecture 5.

15. ASTR 330: The Solar System Fly-by missions Dr Conor Nixon Fall 2006 Fly-by missions are always the first scouts sent to a planet, on a basic reconnaissance assignment. They are built cheaply with a few basic instruments to measure magnetic field properties and image the surface, paving the way for later, more capable orbiters and landers. It would be impossible to design a successful orbiter, let alone a lander, without basic knowledge of planet provided by fly-by missions. We will discuss some famous robotic fly-bys, but note that Apollo 8 was also famous as the first manned fly-by mission of another world (the Moon).

16. ASTR 330: The Solar System First Lunar Fly-bys Dr Conor Nixon Fall 2006 The USSR in 1959 achieved the first successful lunar fly-by with 361-kg Luna 1 (top right). Luna carried radio equipment, and five scientific experiments. This spacecraft discovered the solar wind, and flew by the Moon at 6000 km after 34 hours of flight, finding no magnetic field. Luna 1 now orbits the Sun. Picture credit: NASA/NSSDC The Luna 3 flyby of 1959 is also notable, as it returned the first pictures of the lunar far-side (lower right). Luna 3 used solar cells for power, and had an onboard photographic film processing unit, combined with a ‘fax machine’ which scanned and relayed the images to the Earth. The spacecraft was directly controlled by radio from the ground.

17. ASTR 330: The Solar System First Venus Flyby Dr Conor Nixon Fall 2006 The first close-up survey of Venus was made by the US Mariner 2 spacecraft (December 1962, upper right). Marin. 2 had a hexagonal chassis, which contained most of the power, command and control sub-systems. The mast carried the scientific experiments. Below the body were solar panels extending 5-m in width, and a directional dish antenna. Picture credit: NASA/NSSDC On arrival at Venus, Mariner 2 scanned the planet with infrared and microwave detectors, showing a high surface temperature and pressure, no magnetic field, a backwards (retrograde) rotation, and making important measurements of the solar wind and astronomical unit. Mariner 2 is also noted as the first successful spacecraft encounter with another planet.

18. ASTR 330: The Solar System First Mars Fly-by Missions Dr Conor Nixon Fall 2006 We have already discussed the Mariner Mars missions in an earlier class (L16). Mariner 4 flew by in 1965, taking the first close-up pictures and seeing many craters, but missing the great Tharsis volcanoes and other interesting features. It was the first spacecraft to successfully image a planet. Mariners 6 and 7 (1969) were also flyby missions. Picture credit: solarviews.com

19. ASTR 330: The Solar System Voyager 1 & 2 Dr Conor Nixon Fall 2006 By far the most well-known and ground-breaking fly-by missions of all time were the twin Voyager 1 & 2 spacecraft, discussed in detail earlier in the course. In fact, Pioneers10 & 11 had already reached Jupiter (and Saturn for Pioneer 11). Picture credit: NASA/NSSDC The Voyager missions were famous for achieving the grand tour: the multiple flybys of all four gas giant planets that was achieved by Voyager 2.

20. ASTR 330: The Solar System Orbiter missions Dr Conor Nixon Fall 2006 Orbiter missions follow on from fly-by missions. Their purpose is usually to obtain a thorough mapping of the planetary surface, mostly in visible light, although sometimes radar must be used. The ideal orbit for this is a polar orbit, passing over both poles, and mapping the planet as a rotates underneath each orbital track - this is often used for the Earth. For planetary missions however, it is often too difficult or expensive to reach a polar orbit, so orbiters are in equatorial or low-inclination orbits.

21. ASTR 330: The Solar System First Lunar Orbiters Dr Conor Nixon Fall 2006 Luna 10 was the first successful lunar orbiter, entering orbit on April 4th 1966. Luna 10 carried a whole suite of scientific instruments, including gamma ray, magnetic field, plasma, meteorite, and infrared detectors. It lasted for 460 orbits (about 2 months). Other ‘Luna’ orbiters followed. Picture credit: NASA/NSSDC The US followed up on Ranger with the 5 Lunar Orbiter missions (1966-1967), whose primary purpose was map the Moon for possible manned landing sites. As with Luna, LO used a combination off photographic film, processor, and scanner which succeeded in mapping 99% of the Moon with 60 m precision, and some areas down to 2 m accuracy.

22. ASTR 330: The Solar System Mariner 9 Dr Conor Nixon Fall 2006 Mariner 9 of course was the orbiter which arrived during a dust storm, but stayed around long enough to find most of the exciting topography. Mariner 9 was also the first spacecraft to successfully orbit another planet, and took the first good pictures of Phobos and Deimos. Picture credit: NASA/NSSDC The spacecraft was built on an octagonal magnesium frame, with four solar panels having a total area of almost 8 m 2, and providing 500 W of power at Mars. The total mass was 1000 kg, nearly half of which was fuel. The instruments were mounted on the bottom of the frame: cameras, infrared radiometer and spectrometer, UV spectrometer.

23. ASTR 330: The Solar System Vikings 1 & 2 Dr Conor Nixon Fall 2006 One of the most ambitious and costly ($1bn) robotic planetary missions ever was also one of the most successful. The dual Viking orbiters/landers (2 of each) arrived at Mars in 1976, whereupon the orbiters spent 1 month mapping the surface to find good sites for the landers, which were then released. Picture credits: NASA/NSSDC V1 orbiter lasted until 1980, and V2 orbiter until 1978 - both limited by fuel supply. A huge amount of pictures and other data was returned. The orbiters alone weighed 900 kg. Can you see any resemblances to the Mariner spacecraft?

24. ASTR 330: The Solar System Radar Mapping Mapping Dr Conor Nixon Fall 2006 Venus poses a tougher problem for mapping than the Moon or Mars - why? Due to the dense, cloudy atmosphere, mapping in visible light will not se to the surface - radar must be used. The best ever surface map of Venus was made by the Magellan spacecraft (artist’s impression, right), which used an advanced form of radar called ‘synthetic aperture radar’ (SAR) to map the entire planet down to 100 m resolution. The task took 2 years, from 1990-1992, and Magellan finally returned more data than all previous missions combined! Picture credit: NASA/JPL

25. ASTR 330: The Solar System Recent Orbiters Dr Conor Nixon Fall 2006 A good example of a recent, focused lunar mapper was the DOD Clementine spacecraft launched in 1994. In 1996, mission scientists reported finding ice at the lunar S. Pole. This will soon be followed by Lunar Reconnaissance Orbiter (LRO) in 2008, which will focus on mapping water and landing sites near the South Pole. Many spacecraft are currently in Martian orbit, including: Mars Global Surveyor (just died last month), Mars Reconnaissance Orbiter Mars Odyssey Mars Express

26. ASTR 330: The Solar System Atmospheric Probes Dr Conor Nixon Fall 2006 Atmospheric probes were not relevant to the exploration of the Moon or Mars, but especially for Venus there were many atmospheric probes (attempted landers for the most part) before a true landing was achieved. In the outer solar system, Galileo carried a probe (no name) which was dropped into Jupiter’s atmosphere, returning the first in situ measurements of the temperature and composition of a gas giant world.

27. ASTR 330: The Solar System Venus Atmospheric Probes Dr Conor Nixon Fall 2006 Early Soviet Venera missions concentrated on probing the atmosphere in preparation for an eventual landing on the surface. The first probe to enter Venus’s atmosphere, Venera 4 (1967, right) was crushed in the atmosphere, but showed a surface temperature of 770 K, pressure 75 bars, and an atmosphere of 90-95% CO 2. Picture credit: NASA/NSSDC The Venera 4 probe carried 2 thermometers, a barometer, pressure gauge, 11 gas analyzers etc. Veneras 5&6 (1969, left) were also crushed, 26 and 11 km from the surface respectively. The 405 kg entry probes were strengthened versions of Venera 4. During these descent, measurements of atmospheric composition, temperature and pressure were further refined.

28. ASTR 330: The Solar System Landers Dr Conor Nixon Fall 2006 The second wave of lunar missions in the early 1960s, following the early flybys, but preceding the orbiter missions, were simple impact-trajectory craft designed to photograph the surface right up to the point of impact. In just a few years however, these missions progressed to soft landers, paving the way for eventual human landings in 1969. Soft-landers are able to relay vital information about the surface properties of a planet, especially surface texture, slope, firmness etc - and then continue to function as ‘weather stations’ (on Mars) or seismometers (on the Moon).

29. ASTR 330: The Solar System First Lunar Soft Landings Dr Conor Nixon Fall 2006 While the US struggled with its Ranger program of impact-trajectory craft, the USSR was developing landers. Luna 5 through 8 were failed soft landers (most impacted the Moon, although Luna 6 missed the Moon. Luna 9 (upper right) was successful however. This 100-kg spacecraft made the first soft landing on the Moon on January 31st 1966. Picture credit: NASA/NSSDC On landing, the four ‘petals’ sprung open, and stabilized the spacecraft. Spring-controlled antennas lifted up. A moveable mirror system reflected a 360-degree panorama to a television camera mounted inside. The first close-up pictures of the lunar surface enabled the study of craters sizes and shapes, ejecta amounts and distribution, and surface properties.

30. ASTR 330: The Solar System US First Lunar Landers Dr Conor Nixon Fall 2006 NASA’s first successful soft lander was the 270-kg Surveyor 1 (right) on June 2nd, 1966. Six more Surveyors were launched between 1966 and 1968. The Surveyors were all equipped with television cameras, and later carried a variety of soil measuring devices. In all, 88,000 high resolution pictures were returned. A primary objective of the Surveyor missions was to test whether the surface was safe for manned landings. The mosaic image (right) was taken by Surveyor 7 in 1968 of the Tycho crater region. Picture credit: NASA/NSSDC

31. ASTR 330: The Solar System First Venus Landings Dr Conor Nixon Fall 2006 Picture credit: NASA/NSSDC Venera 7 (1970, left) was the first successful landing on another planet sending back 23 minutes of data. The surface conditions were correctly measured: 90 bars and 750 K. Venera 7 used aerodynamic braking and a parachute to slow the descent, and an external cooling device (refrigeration) prevented overheating. Venera 8 (1972) was a modified version of Venera 7. Aero-braking slowed the craft from 42,000 km/h to 900 km/h. A 2.5-m chute opened at 60 km altitude. Venera 8 measured wind speeds during descent and survived the surface for 50 minutes. It showed that surface light level were about the same as the Earth on an overcast day, despite the unbroken clouds.

32. ASTR 330: The Solar System Later Venus Landings Dr Conor Nixon Fall 2006 The early Venera landers did not return images, only meteorological data from the surface. That changed in 1975, when the twin Venera 9 and 10 missions (upper left) sent back the first B&W pictures of the surface. Each lasted about 1 hour. Veneras 11&12 followed in 1978, lasting up to 2 hours. Veneras 13&14 (1981, lower left, 760 kg) returned the first color pictures of the surface. They also conducted soil analysis, finding different types of basalt at the two locations. What do you think is the function of the (i) cylinders with spirals, at top (ii) disk-shapes, next down (iii) spherical lower parts (iv) ring- shaped lower parts? Picture credit: NASA/NSSDC

33. ASTR 330: The Solar System Viking 1 & 2 Landers Dr Conor Nixon Fall 2006 The huge landers (600 kg each) contained entire weather stations which remained active for 6 years (Viking 1) and 4 years (Viking 2), much longer than anticipated. Both could communicate with the orbiters, or directly with the Earth by radio. Why? Landing was accomplished by 3 retrorockets with 18 nozzles each, to minimize disturbance of the surface. Even the N 2 H 4 fuel was purified! Picture credit: NASA/JPL Power was supplied by 2 small Plutonium RTG units, good for 30 W each. Why were RTGs used, rather than solar cells? One of the main objectives was to search for life. The results of this complex experiment are still being debated!

34. ASTR 330: The Solar System Huygens Probe: Entry Subsystem Dr Conor Nixon Fall 2006 The Huygens probe has one main challenge which the Cassini orbiter will not need to be concerned about: entry into Titan’s atmosphere. What types of protection and braking might be required? The probe separates from the orbiter on Christmas Day 2004, coasts through space for 22 days, before reaching Titan. The initial entry speed is 6 km/s, nearly 14,000 mph. During this phase, lasting 3 minutes, the probe is protected by a heat shield. The temperature in front of the shield reaches 12,000 C (21,600 F). After three minutes the speed is reduced to 400 m/s (895 mph) at which time the main parachute deploys. After 15 more minutes, the main chute is releases and the probe then drifts down to the surface under a smaller drogue chute, arriving at the surface after 2.5 hrs.

35. ASTR 330: The Solar System Huygens Titan Entry Dr Conor Nixon Fall 2006 Picture credit: JPL

36. ASTR 330: The Solar System Rovers Dr Conor Nixon Fall 2006 Rover missions are the next logical step in surface exploration after a lander: effectively a rover is a mobile lander, which can carry out the science of dozens of landers at different locations. When we think of rovers today we think of Mars rovers, but these were preceded by lunar rovers. At around the same time that US astronauts were driving lunar rovers, the USSR was controlling robotic rovers, which

37. ASTR 330: The Solar System Later Luna Missions Dr Conor Nixon Fall 2006 The Luna 17 mission (1970, right) was the first USSR mission to deploy a rover on the moon. Looking like a bathtub on wheels, Lunokhod 1 was intended to last for 3 lunar days, it lasted 11 (322 Earth days), traveling 10 km, returning 20,000 pictures and conducting 500 soil samples. The Luna 21 mission also carried a Lunokhod rover. Picture credit: NASA/NSSDC Lunas 20 (1972) and 24 (1976, right) were sample return missions. They returned 20 and 170 grams of lunar rock material to the Earth for study. Of course, by then Apollo had far eclipsed these achievements.

38. ASTR 330: The Solar System Pathfinder Rover - Sojourner Dr Conor Nixon Fall 2006 The first successful mobile Mars robot, Pathfinder was low-cost technology demonstration mission. A combination of chutes, airbags and retrorockets were used to slow and land the robots. Pathfinder consisted of a lander and the small (10 kg) 6-wheeled rover, the size of a microwave oven, named Sojourner. Picture credit: NASA/NSSDC The Rover returned 550 pictures, and over 16,000 were returned by the main lander. 15 rock/soil assays were also completed by Sojourner. Pathfinder lasted for 83 days in 1996, until communication was lost for unknown reasons.

39. ASTR 330: The Solar System Bigger Bots On Mars Dr Conor Nixon Fall 2006 The rovers consist of a box on six wheels, each independently powered and the front and rear wheels steerable. The mast contains the camera, and an arm attached to the main box holds other sensors. The robot can communicate with the Earth via high or low gain antennas. Note the solar panels, which provide a peak power of 140 W. Picture credit: NASA/NSSDC The Mars Spirit and Opportunity rovers (MERs) of 2003 are much larger vehicles, weighing 185 kg and about the size of a golf cart. These machines can travel 100 meters per day, a top speed of 5 cm/s! Although they will usually travel much slower due to collision avoidance. The main science objective is geology, especially traces of water.

40. ASTR 330: The Solar System Hybrid Missions Dr Conor Nixon Fall 2006 As successes accumulated, mission planners became increasingly adventurous with future plans. Later landers carried rovers, such as Luna/Lunokhod on the Moon, and Pathfinder/Sojouner on Mars. Another combination was the orbiter/lander or orbiter & atmospheric probe combination. In the inner solar system, this approach was used many times at Venus (Venera), and also at Mars (Viking). In the outer solar system, we have Galileo and Cassini/Huygens.

41. ASTR 330: The Solar System Pioneer Venus Dr Conor Nixon Fall 2006 Pioneer Venus was a ground-breaking US Venus mission in 1978. The mission consisted of two spacecraft, an orbiter and a lander. The orbiter was described in an earlier lecture, and made an improved radar map of the surface. Fuel ran out and it burned up in 1992. The lander was actually a multi-probe in 4 parts. The main bus was unprotected, and burned up at 110 km altitude after making some photos. The bus released 3 miniature spherical probes (80 cm) which spread out to impact (no parachutes!) on different parts of the planet. One survived landing, but all relayed back atmospheric data: temperature, pressure and net radiative flux. Picture credit: NASA/NSSDC

42. ASTR 330: The Solar System Taking a Balloon Ride Dr Conor Nixon Fall 2006 Perhaps the most eclectic mission of all time were the twin Vega 1 & 2 missions (French-USSR partnership) launched in 1984, to Comet Halley and Venus. Each Vega Mission consisted of 3 distinct spacecraft. The main spacecraft were the comet-catchers, which in June 1985 flew by Venus and gained a gravity assist to continue on to the comet. Picture credit: NASA/NSSDC At Venus, a Venera-style lander was dropped, which requires no further elaboration. In addition, a 3.4 m meteorological balloon was deployed by each Vega which floated in the atmosphere at 50-km altitude, lasting for 2 days. On reaching the dayside they overheated and burst (as planned).

43. ASTR 330: The Solar System Outer Solar System Exploration Dr Conor Nixon Fall 2006 Exploring the outer solar system presents a unique set of difficulties. 1.Timescales for missions are long, and so components must be reliable. 2.Power is also a major consideration. Can solar power can be used? Very few spacecraft have been launched to the outer planets, at least partly due to the cost and timescales of such missions. Pioneer 10 & 11 Voyager 1 & 2 Ulysses Galileo and Cassini

44. ASTR 330: The Solar System Instruments Dr Conor Nixon Fall 2006 Cassini carries a large number of scientific experiments: 12 on the orbiter, and a further 6 on the Huygens probe. These include both remote sensing instruments (camera, IR spectrometers etc) and in situ experiments such as dust collectors. Picture credit: JPL The spacecraft carries a radar-mapper, and the high- gain antenna does double- duty as a radio occultation experiment. The probe carries instruments to image the surface, detect and measure gas types and concentrations, aerosols and dust and more.

45. ASTR 330: The Solar System Instruments 1: Remote Sensing Dr Conor Nixon Fall 2006

46. ASTR 330: The Solar System Instruments 2: In Situ Dr Conor Nixon Fall 2006

47. ASTR 330: The Solar System Quiz-Summary Dr Conor Nixon Fall 2006 1.When did we first see the far side of the Moon, and how? 2.What were the main problems encountered when trying to land and operate a spacecraft on Venus, and how were these overcome? 3.Describe what other types of missions have been sent to Venus, other than single landers and orbiters. 4.How has exploration of Mars changed from Mariner 2 (1965) to the present day? What technologies are possible now that were not then.