CURIOSITY ROVER – MARS EXPLORATION

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CURIOSITY ROVER MARS EXPLORATION

• Supervised By Dr. Mohammad Zaki Kheder
• Done By Mohammad Taiseer Khorma

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SUBJECTS OUTLINE

• INTRODUCTION

• CURIOSITY ROVER

• MARS, The Red Planet
• Why Exploring MARS?
• MARS Exploration History
• Why Rovers Not Astronauts?

• Overview of Curiosity rover trip dates,
  dimensions and cost
• Electrical Drive System
• Motors
• Power Supply
• Gears
• Curiositys Computer
• Other parts and subsystems

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INTRODUCTION

• MARS, The Red Planet
• Why Exploring MARS?
• MARS Exploration History
• Why Rovers Not Astronauts ?

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MARS

• Mars is the fourth planet from the Sun and the
  second smallest planet in the Solar System
• It is often described as the "Red Planet", as the
  iron oxide prevalent on its surface gives it a
  reddish appearance
• Mars is a terrestrial planet with a thin
  atmosphere
• Mars has two moons, which are small and
  irregularly shaped
• Mars can easily be seen from Earth with the naked
  eye

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WHY EXPLORING MARS ?

• The rotational period and seasonal cycles of Mars
  are likewise similar to those of Earth (Martian
  day about 24 hour and 35 min)
• Exploring existence of life and its
  constituents, which include
• Searching of Water
• Study Martians chemical elements and geology
• Study the weather and radiation

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MARS EXPLORATION HAS HISTORY

• Since 1960, many exploration attempts took place
• The attempts took several forms, like orbiters,
  Landers or rovers
• They were total of 50 attempts, 21 of them
  succeed and the rest failed in lunching or
  landing (or orbiting)
• Since 2004 up to now, three Rovers have reached
  MARS land, one of them breakdown and remaining
  two are still doing their jobs

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WHY ROVERS NOT ASTRONAUTS ?

• Although human are much more intelligent than
  robots, sending robots is better because
• Such trips are very dangerous to human
• Sending rovers need lower cost because it doesnt
  need food, water, like human
• Also there is no need to return the rover back to
  earth after finishing its jobs which eliminate
  the complexity and cost of back trip

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CURIOSITY ROVER

• Overview of Curiosity rover trip dates,
  dimensions and cost
• Electrical Drive System
• Motors
• Power Supply
• Gears
• Curiositys Computer
• Other parts and subsystems

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CURIOSITY ROVER

• The Curiosity rover is a car-sized robotic rover
  exploring Gale Crater on Mars as part of NASA's
  Mars Science Laboratory mission

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CURIOSITY ROVER

• This rover is doing its jobs on Mars now
• Its spacecraft has been lunched on November 26,
  2011
• It landed safely on August 5, 2012, after 560
  million-km journey
• It took eight years of building and testing

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MASS DIMENSIONS

• Curiosity rover has a mass of 899 kg (1,980 lb)
  including 80 kg (180 lb) of scientific
  instruments
• The rover is 2.9 m (9.5 ft) long by 2.7 m (8.9
  ft) wide by 2.2 m (7.2 ft) in height
• Wheel diameter 0.5 meter (20 inches)

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PROJECT COST

• Curiosity had a total cost of 2.5 billion dollars
• 820 million dollars were cost of building,
  launching, landing and operating the rovers on
  the surface for the initial 90-Martian-day
• 7000 people work on Curiosity at various times
  over the last eight years

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ELECTRICAL DRIVE SYSTEM

1. Motors 43 DC motors are used, part of them are
   Brushless DC motors (ECM motors)
2. Power Supply Multi-Mission Radioisotope
   Thermoelectric Generator (Nuclear Generator)
   supplying two rechargeable Batteries
3. Gears Harmonic Drive system

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MOTORS IN CURIOSITY

• Most of space rovers (including Curiosity) use
  Maxon motors, because of their enhanced features
• Small size (diameters of 20mm and 25mm )
• Can withstand temperatures between -120 and 25
  Celsius
• High efficiency up to 90

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MOTORS IN CURIOSITY

• But that performance has a price, with Maxon
  motors costing up to five times that of
  conventional motors.
• In Curiosity, the motors are used for driving the
  robotic arms, rock drilling, the steering
  mechanism, controlling the cameras and for the
  six high-tech wheels that drive the heavy rovers,
  each weighing nearly 180 kilos.

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Brushless DC Motor ECM Motor

• Using Programmable Controller include features
  like data communications, constant volume
  control, variable speed
• ECM motors are very high efficiency 65 to 80
  (without heat losses in rheostat speed
  controller) which means that the motors run
  cool, and also typically translates in reduced
  operation at the compressor level, which allows
  further energy savings.
• have longer design life and require less
  maintenance
• ECM motors are more expensive than traditional
  inefficient motors

• Electronically commutated (ECM) motors are
  brushless DC motors where the direction of the
  electric current is switched using electronic
  controllers.ECM motors provide the advantages of
  brushed DC motors in terms of the ability to have
  variable speed control, but without the drawbacks
  of brushes.ECM motors have longer lives than
  other types, the reason of using them in
  Curiosity.

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Multi-Mission Radioisotope Thermoelectric
Generator

• RTGs can provide continuous power for twenty-plus
  years, in a safe and reliable manner, the reason
  of using it on Curiosity.
• RTGs work by converting heat from the natural
  decay of radioisotope materials into electricity.
  
• RTGs consist of two major elements
• Heat source
• Thermocouples

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Multi-Mission Radioisotope Thermoelectric
Generator

• Plutonium 238

• Thermocouple

• A radioisotope material with unstable nucleus
  atoms resulting in the emission of gamma ray and
  heat

• Convert thermal power to electrical power.
  Consist of two dissimilar, electrically
  conductive materials which are joined in a closed
  circuit and the two junctions are kept at
  different temperatures (Seebeck effect)

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MMRTG IN CURIOSITY

• Curiosity's RTG is fueled by 4.8 kg of
  plutonium-238 dioxide
• It is designed to produce 125 watts of electrical
  power from about 2000 watts of thermal power at
  the start of the mission, and less power over
  time as its plutonium fuel decays (at its
  minimum lifetime of 14 years, electrical power
  output is down to 100 watts)
• Unfortunately, thermoelectric generators are
  notoriously inefficient as their efficiency level
  is about 6.2.
• However, MMRTG produces much more than the solar
  panels of the previous Mars Exploration Rovers

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MMRTG IN CURIOSITY

• MMRTG consist of eight General Purpose Heat
  Source (GPHS) modules.
• Each GPHS module with plutonium-238 dioxide will
  provide approximately 250 watts of thermal power.
• Several layers of protective material designed to
  contain the plutonium-238 fuel

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MMRTG IN CURIOSITY

• The thermocouples in RTGs use heat from the GPHS
  to heat the hot junction of the thermocouple, and
  use the cold of outer space to produce a low
  temperature at the cold junction of the
  thermocouple
• The electrical output from the MMRTG charges two
  rechargeable lithium-ion batteries. This enables
  the power subsystem to meet peak power demands of
  rover activities when the demand temporarily
  exceeds the generators steady output level. Each
  battery has a capacity of about 42 amp-hours

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GEARS IN CURIOSITY

• Harmonic drive gears used in Curiosity to enjoy
  they improved characteristics over traditional
  gears
• Harmonic drives are ideally suited for use when
  high precision actuator operation is required.
  Additionally, harmonic drives provide a very high
  degree of repeatability of movement, since it has
  zero freeplay or backlash
• Harmonic Drive which was developed to take
  advantage of the elastic dynamics of metal -- is
  generally made up of just three components a
  wave generator, a flexspline and a circular
  spline

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HARMONIC DRIVES

• The wave generator is a component having small
  ball bearings built into the outer circumference
  of the elliptical cam. The inside raceway of the
  bearings is fixed to the cam while the outer
  raceway is subjected to elastic deformation via
  the ball bearings. The wave generator is usually
  attached to the input shaft
• The flexpline is a thin cup-shaped metal rim
  component with external teeth. The bottom of the
  flexspline (cup bottom) is called the diaphragm.
  The diaphragm is usually attached to the output
  shaft
• The circular spline is a rigid steel ring with
  internal teeth. The circular spline has two teeth
  more than the flexpline and is usually fixed to a
  casing

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HARMONIC DRIVES
The flexspline is deflected by the wave generator
into an elliptical shape causing the flexspline
teeth to engage with those of the circular spline
at the major axis of the wave generator ellipse,
with the teeth completely disengaged across the
minor axis of the ellipse.

• When the wave generator is rotated clockwise with
  the circular spline fixed, the flexspline is
  subjected to elastic deformation and its tooth
  engagement position moves by turns relative to
  the circular spline.

When the wave generator rotates 180 degrees
clockwise, the flexspline moves counterclockwise
by one tooth relative to the circular spline.
When the wave generator rotates one revolution
clockwise (360 degrees), the flexspline moves
counterclockwise by two teeth relative to the
circular spline because the flexspline has two
fewer teeth than the circular spline.
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HARMONIC DRIVES

• Characteristics of Harmonic drives

• High-speed reduction ratio with single-stage
  coaxial provides high efficiency gearing without
  using complex mechanisms and structures.
• 2. Free of backlash (lost motion)
• 3. High precision

• 4. Small numbers of components and ease of
  assembly
• 5. Small-sized and lightweight
• 6. High torque capacity
• 7. High efficiency
• 8. Quiet, vibration-free operation

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CURIOSITYS BRAIN

• At the heart of Curiosity there is, of course, a
  Computer
• Designed for autonomous rover
• Hardware
• Two identical RAD750 board one of them is backup
• Each computer's memory includes 256 kB of EEPROM,
  256 MB of DRAM, and 2 GB of flash memory
• 200MHz CPU, capable of up to 400 MIPS

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CURIOSITYS BRAIN

• Software
• VxWorks operating system
• 27-year-old but developed yearly
• Why does Curiosity use it?
• Its reliable, has a mature development
  toolchain, and presumably its low-level
  scheduling and interrupt systems are ideal for
  handling real-time tasks like EDL (entry,
  descent, and landing aka, seven minutes of
  terror).

• Functioning code
• Language C is used
• It's 3.5 million lines of code
• much of it autogenerated by simulation programs
  but over a million lines were hand coded
• The code is implemented as 150 separate modules
• All activities are controlled by this computer,
  like self-monitoring, taking pictures, driving,
  navigation, and other operation.

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CURIOSITYS BRAIN

• On Mars, very high level of radiation and very
  low level of temperature take place, which can
  not be withstood by traditional processors
• In fact, Curiositys computer is virtually
  impervious to massive amounts of radiation and
  other environmental extremes.
• The immunity of processor of radiation put a
  strict limitation on its capabilities and
  performance, the reason behind that Curiositys
  processor has abilities 10 times less than a
  smart phone nowadays!
• Therefore, a software update has done after the
  landing on Mars flushing out the no-longer-needed
  entry, descent and landing application and
  replacing them with software optimized for
  surface operations

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OTHER PARTS AND SUBSYSTEMS

• Curiosity is quite literally a science lab on
  wheels!

• Mobility Systems
• Heat Rejection System
• Communication System
• Robotic Arm
• Mast Camera (MastCam)
• Chemistry and Camera complex (ChemCam)
• Navigation Cameras (Navcams)
• Hazard Avoidance Cameras (Hazcams)

• Radiation Assessment Detector (RAD)
• Mars Hand Lens Imager (MAHLI)
• Alpha Particle X-ray Spectrometer (APXS)
• Chemistry and Mineralogy (CheMin)
• Sample Analysis at Mars (SAM)
• Mars Descent Imager (MARDI)

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Mobility Systems

• Curiosity is equipped with six 50 cm diameter
  wheels in a rocker-bogie suspension
• Legs made of titanium tubing
• Wheels made of aluminum, with cleats for traction
• It can travel up to 90 meters (295 feet) per hour
  but average speed is about 30 meters per hour

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Mobility Systems

• This steering capability allows the vehicle to
  turn in place, a full 360 degrees
• The rover is capable of climbing sand dunes with
  slopes up to 12.5 degrees
• Based on the center of mass, the vehicle can
  withstand a tilt of at least 50 degrees in any
  direction without overturning
• Curiosity will be able to roll over obstacles
  approaching 65 cm (26 in) in height
• It can travel up to 90 meters (295 feet) per hour
  but average speed is about 30 meters per hour

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Mobility Systems

• This mobility system requires that each wheel be
  driven by a separate motor and steering mechanism
  (independently actuated and geared) increasing
  the overall complexity.
• Rovers that use the rocker bogie suspension can
  have 10 or 12 motors just for mobility
• Harmonic drives coupled to the motors are used to
  increase torque capacity and save space and
  weight

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Heat Rejection System

• The temperatures at the landing site can vary
  from -127 to 40 C
• HRS controls temperature so that sensitive
  components are kept at optimal temperatures
• The thermal system will achieve this by gathering
  waste heat from the power source and dissipation
  of internal components to heat fluid in body
  tubes
• The fluid pumped through 60 m (200 ft) of tubing
  in the rover body in a measured way to get
  specific temperature
• The HRS also has the ability to cool components
  if necessary

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Communication System

• Curiosity is equipped with significant
  telecommunication redundancy by several means -
  it can communicate directly with Earth, or using
  UHF for communicating with Mars orbiters.
• Communication with orbiters is expected to be the
  main path for data return to Earth, since the
  orbiters have both more power and larger antennas
  than the rover allowing for faster transmission
  speeds
• An average of 14 minutes, 6 seconds will be
  required for signals to travel between Earth and
  Mars.
• Curiosity can communicate with Earth directly at
  speeds up to 32 kbit/s

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Communication System
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Robotic Arm

• The rover has a 2.1 m long arm with holding five
  devices that can spin through a 350-degree
• The arm makes use of three joints to extend it
  forward and to stow it again while driving
• It has a mass of 30 kg and its diameter is about
  60 cm
• Two of the five devices are contact instruments
  known as the X-ray spectrometer (APXS), and the
  Mars Hand Lens Imager (MAHLI camera)
• The remaining three are associated with sample
  acquisition and sample preparation functions a
  percussion drill, a brush, and mechanisms for
  scooping, sieving and portioning samples of
  powdered rock and soil
• The diameter of the hole in a rock after drilling
  is 1.6 cm and up to 5 cm deep
• The drill carries two spare bits

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Robotic Arm
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Mast Camera (MastCam)

• The MastCam system provides multiple spectra and
  true-color imaging with two cameras
• The cameras can take true-color images at
  16001200 pixels and up to 10 fps and video at
  720p (1280720)
• Each camera has 8 GB of flash memory, which is
  capable of storing over 5,500 raw images, and can
  apply real time lossless data compression
• The cameras have an autofocus capability that
  allows them to focus on objects from 2.1 m (6 ft
  11 in) to infinity

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Chemistry and Camera complex

• ChemCam is a suite of remote sensing instruments,
  its actually two different instruments combined
  as one a laser-induced breakdown spectroscopy
  (LIBS) and a Remote Micro Imager (RMI) telescope.
• The purpose of the LIBS instrument is to provide
  elemental compositions of rock and soil, while
  the RMI will give ChemCam scientists
  high-resolution images of the sampling areas of
  the rocks and soil that LIBS targets
• The LIBS instrument can target a rock or soil
  sample from up to 7 meters away

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Navigation Cameras (Navcams)

• The rover has two pairs of black and white
  navigation cameras mounted on the mast to support
  ground navigation
• The cameras have a 45 degree angle of view and
  use visible light to capture stereoscopic
• 3-D imagery
• These cameras support use of the ICER image
  compression format.

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Hazard Avoidance Cameras

• The rover has four pairs of black and white
  navigation cameras called Hazcamstwo pairs in
  the front and two pairs in the back
• They are used for autonomous hazard avoidance
  during rover drives and for safe positioning of
  the robotic arm on rocks and soils
• The cameras use visible light to capture
  stereoscopic three-dimensional (3-D) imagery
• The cameras have a 120 degree field of view and
  map the terrain at up to 3 m in front of the
  rover
• This imagery safeguards against the rover
  crashing into unexpected obstacles, and works in
  tandem with software that allows the rover to
  make its own safety choices

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Radiation Assessment Detector

• This instrument was the first of ten instruments
  to be turned on. Its first role was to
  characterize the broad spectrum of radiation
  environment
• RAD main purpose is to determine the viability
  and shielding needs for potential human
  explorers. Its second role is to characterize the
  radiation environment on the surface of Mars,
  which it started doing immediately after landing

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Mars Hand Lens Imager (MAHLI)

• "Magnifying Eye, much like a geologist's hand
  lens, this camera provides close-up views of
  minerals, textures, and structures in Martian
  rocks at scales smaller than the diameter of a
  human hair
• That information will help us understand if any
  rocks formed in water, which is necessary to life
  as we know it. It will help scientists select
  which rocks may be the best to study
  further--that is, rocks and minerals that may
  contain signs of organics, the chemical building
  blocks of life.
• With two white LED lights, it can take pictures
  at night, and with ultraviolet (UV) LEDs, can
  look for minerals that fluoresce
• It can also send high-definition video back to
  Earth and even be used to look back to take a
  self-portrait of Curiosity.

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Alpha Particle X-ray Spectrometer

• This tool helps identify the chemical elements in
  rocks and soil and tells us how much of each is
  present
• Identifying the elemental composition of lighter
  elements (sodium, magnesium or aluminum) and
  heavier elements (iron, nickel or zinc) helps
  scientists identify main materials in the Martian
  crust
• This information helps scientists select rock and
  "soil" samples, characterize the interiors of the
  rocks following brushing, and then determine how
  the material formed long ago and if it was later
  altered by wind, water, or ice. All previous
  rovers have carried a tool like this one, so
  comparisons of landing sites can be made to
  understand the history of Mars even better

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Chemistry and Mineralogy

• Finding minerals that either formed in water or
  were altered by water in the past helps us
  understand if Mars ever could have been a habitat
  for microbes
• This tool is one of two instruments that studies
  powdered rock and soil samples scooped up by the
  robotic arm
• Curiosity uses it to tell us what kinds of
  minerals are in samples and how much of them are
  there
• Minerals provide a record of what happened in the
  past
• Different minerals are linked to certain kinds of
  environments.

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Sample Analysis at Mars (SAM)

• Curiosity uses this tool to search for organics,
  carbon-based molecules that are the chemical
  building blocks of life
• Finding organics is important in the search for
  Martian environments capable of supporting
  microbes, because life as we know it cannot exist
  without them (though they can exist without life)
• This tool allows Curiosity to detect lower
  concentrations of a wider variety of organic
  molecules than any other instrument yet sent to
  Mars. It is one of two instruments that study
  powdered rock and soil samples scooped up by the
  robotic arm
• Curiosity will deliver powdered samples to one of
  two funnels on the rover deck ("back") and then
  to small cups for processing inside the rover's
  "body." Finding evidence that Gale Crater had
  both past water and organics would suggest it
  might have been hospitable to life

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Mars Descent Imager (MARDI)

• Ever wonder what it would be like to have an
  "astronauts" view of landing on Mars? Finishing
  its job in the seconds before landing, this
  camera shoots full-color video of Curiosity's
  journey through the atmosphere all the way down
  to the Martian surface.
• This camera may give the science team and rover
  drivers a glimpse of the landing site to aid them
  in accurately identifying Curiosity's landing
  spot and in planning the rover's first drives
• One of its main jobs is helping the mission team
  locate loose debris, boulders, cliffs, and other
  features in the terrain that pose potential
  hazards to the rover and should be avoided.

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