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ASTR 330: The Solar System

ASTR 330: The Solar System. 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.

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ASTR 330: The Solar System

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  1. ASTR 330: The Solar System • 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/ Announcements Dr Conor Nixon Fall 2006

  2. ASTR 330: The Solar System 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. Space Mission Game! Dr Conor Nixon Fall 2006

  3. ASTR 330: The Solar System The class will be divided into groups of 6-7, in teams. Each team will be required to: 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. Prepare a presentation to the class. At least two team members must present. Presentations should take about 3 minutes or less. Space Mission Game! Dr Conor Nixon Fall 2006

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

  5. ASTR 330: The Solar System 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. Judging and Scoring Dr Conor Nixon Fall 2006

  6. ASTR 330: The Solar System • Final exam: Tuesday December 19th, 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. Exams Dr Conor Nixon Fall 2006

  7. ASTR 330: The Solar System 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. Exam conduct Dr Conor Nixon Fall 2006

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

  9. ASTR 330: The Solar System • 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 addreplacement 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. Example True/False Question Dr Conor Nixon Fall 2006

  10. ASTR 330: The Solar System • 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. True/False continued Dr Conor Nixon Fall 2006

  11. ASTR 330: The Solar System • All four of the outer gas giant planets have ring systems. • Describe the A, B and C rings of Saturn. Say which is the most and least bright, and what the rings are made of. • 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. • 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. Example Structured Question Dr Conor Nixon Fall 2006

  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 No discussion of the planetary system would be complete without examining the technology which supplied most of our information about the planets: roboticspacecraft. 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. Spacecraft Dr Conor Nixon Fall 2006

  14. ASTR 330: The Solar System • Spacecraft missions broadly fall into one of the following categories: • Space Telescopes • Fly-by missions • Orbiter missions • Atmospheric probes (not designed to land). • Hard and soft landers • Rovers. • 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. Types of Spacecraft Missions Dr Conor Nixon Fall 2006

  15. ASTR 330: The Solar System 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). Fly-by missions Dr Conor Nixon Fall 2006

  16. ASTR 330: The Solar System 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). 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. Voyager 1 & 2 Dr Conor Nixon Fall 2006 Picture credit: NASA/NSSDC

  17. ASTR 330: The Solar System 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. Orbiter missions Dr Conor Nixon Fall 2006

  18. ASTR 330: The Solar System 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! Radar Mapping Mapping Dr Conor Nixon Fall 2006 Picture credit: NASA/JPL

  19. ASTR 330: The Solar System 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. Atmospheric Probes Dr Conor Nixon Fall 2006

  20. ASTR 330: The Solar System Early SovietVenera 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% CO2. Venus Atmospheric Probes 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. Dr Conor Nixon Fall 2006 Picture credit: NASA/NSSDC

  21. ASTR 330: The Solar System 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). Landers Dr Conor Nixon Fall 2006

  22. ASTR 330: The Solar System NASA’s first successful soft lander was the 270-kgSurveyor 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. US First Lunar Landers Dr Conor Nixon Fall 2006 Picture credit: NASA/NSSDC

  23. ASTR 330: The Solar System 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 N2H4fuel was purified! Viking 1 & 2 Landers 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! Dr Conor Nixon Fall 2006 Picture credit: NASA/JPL

  24. ASTR 330: The Solar System 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 Rovers Dr Conor Nixon Fall 2006

  25. ASTR 330: The Solar System 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. Later Luna Missions 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. Dr Conor Nixon Fall 2006 Picture credit: NASA/NSSDC

  26. ASTR 330: The Solar System 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. Hybrid Missions Dr Conor Nixon Fall 2006

  27. ASTR 330: The Solar System 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. Pioneer Venus Dr Conor Nixon Fall 2006 Picture credit: NASA/NSSDC

  28. ASTR 330: The Solar System Perhaps the most eclectic mission of all time were the twin Vega 1 & 2 missions (French-USSR partnership) launched in 1984, to Comet Halleyand 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. 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). Taking a Balloon Ride Dr Conor Nixon Fall 2006 Picture credit: NASA/NSSDC

  29. ASTR 330: The Solar System • Exploring the outer solar system presents a unique set of difficulties. • Timescales for missions are long, and so components must be reliable. • 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 Outer Solar System Exploration Dr Conor Nixon Fall 2006

  30. ASTR 330: The Solar System 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. 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. Instruments Dr Conor Nixon Fall 2006 Picture credit: JPL

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

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

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

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