OrbitalHub

NASA’s return to the Moon requires careful preparation. Finding safe landing sites, locating potential resources, and taking measurements of the radiation environment are some of the tasks the Lunar Reconnaissance Orbiter (LRO) spacecraft will perform while in lunar orbit. LRO is an unmanned mission that will create a comprehensive atlas of the moon’s surface and resources.

The data gathered by LRO will be crucial in designing and building a permanent lunar outpost. The data will also be used to reduce the risk and increase the productivity of the future manned missions to the Moon.

The launch of LRO is scheduled for February 2009. An Atlas V rocket launched from the Kennedy Space Center will place the LRO on a transfer trajectory. After 4 days, the spacecraft will reach the Moon and after performing additional orbital maneuvers, it will move into its final orbit. The LRO’s final orbit will be a circular polar orbit 50 kilometers above the lunar surface.

Credits: NASA

The mission is designed to last for one year, with a possible extension. The total mass of the spacecraft is around 1,000 kilograms, of which 500 to 700 kilograms will be the fuel. The power is supplied by articulated solar arrays, and for the peak and eclipse periods a Li-Ion battery is used. The bandwidth of the communication link will be approximately 100-300 Mbps.

The LRO payload is comprised of six scientific instruments and one technology demonstration.

The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) was built and developed by Boston University and the Massachusetts Institute of Technology in Boston. CRaTER will help explore the lunar radiation environment. The data gathered by measurements will help in the development of protective technologies that will keep future lunar crews safe.

The Diviner Lunar Radiometer Experiment (DLRE) was built and developed by the University of California, Los Angeles and the Jet Propulsion Laboratory in Pasadena, California. DLRE is capable of measuring surface and subsurface temperatures from orbit.

The Lyman-Alpha Mapping Project (LAMP) was built and developed at the Southwest Research Institute in San Antonio. LAMP will be used to map the entire lunar surface in the far ultraviolet spectrum.

Credits: NASA

The Lunar Exploration Neutron Detector (LEND) was developed at the Institute for Space Research in Moscow. This detector will create high-resolution maps of the hydrogen distribution and gather data about the neutron component of the lunar radiation.

The Lunar Orbiter Laser Altimeter (LOLA) was conceived and built at NASA’s Goddard Space Flight Center. LOLA will generate high-resolution three-dimensional maps of the moon’s surface.

The Lunar Reconnaissance Orbiter Camera (LROC), developed at Arizona State University at Tempe, will image the lunar surface in color and ultraviolet. LROC will be able to capture 1 m resolution images of the lunar poles.

The technology demonstration is called Mini-RF Technology Demonstration. The primary goal of this demonstration is to locate subsurface water ice deposits. The advanced single aperture radar (SAR) that will be used is capable of taking high-resolution imagery of the permanently shadowed regions on the lunar surface.

The data gathered by LRO will help us develop a better understanding of the lunar environment. This understanding is essential for a safe human return to the Moon and for the future exploration of our solar system.

After a short introduction to the power systems requirements and design factors, we will continue by covering the first solutions adopted by spacecraft designers: the batteries and the solar arrays (aka solar cells).

Credits: NASA

Batteries were used as a primary source of power onboard early spacecrafts. The obvious limitation is that batteries have limited energy storage capabilities and could not keep spacecrafts operational for more then a few days. Most space missions require a reliable power source running for a longer period of time.

Batteries remain the primary means of energy storage onboard spacecrafts. Batteries are divided into two major categories: primary batteries and secondary batteries.

Primary batteries offer higher energy and power densities but are not rechargeable. They are useful for one-time events such as expendable launch vehicle stages. Secondary batteries are rechargeable batteries.

Solar arrays are very well suited for long missions in space. The life expectancy of a solar cell power system is limited only by the degradation of its components. Spacecrafts operating for extended periods of time become feasible with the development of solar arrays. However, if only solar cells are used for generating power, spacecrafts that enter eclipse periods cannot employ only solar cells for power generation.

Credits: NASA

The first low-powered spacecraft designs were using the spacecraft skin for the solar cell deployment. In the case of drum-shaped spacecrafts, only about 40% of the arrays were illuminated by the Sun at any time. Because most of the time the available area on the fixed spacecraft structure is not enough from the standpoint of power requirements, deployable solar arrays are now used. The solar arrays of this type are deployed from the main structure after the spacecraft is injected into orbit.

The deployable panels are designed as extremely lightweight structures due to the fact that they are firmly locked to the spacecraft during the launch. In order to optimize the generation of power, these panels are designed to allow sun tracking.

Credits: NASA

Considering the limitations of the solar arrays, a reliable solution can be reached by employing solar cells and batteries at the same time. Solar arrays can generate power when direct sunlight is available in orbit, while rechargeable batteries can handle peak loads and provide power during eclipse periods. Solar panels and batteries in combination are a common solution used for the unmanned spacecrafts launched to date. The most notable exception is the deep space mission probes using radioisotope thermoelectric generators (we will cover them in a future post).

The early manned spacecrafts, including Mercury, some of the Gemini, and the Russian Vostok /Voshkod vehicles, used batteries. The Russian Soyuz employs solar cells and batteries similar to a typical unmanned spacecraft. The space stations built so far, Salyut, Skylab, Mir, and the International Space Station, have all used solar cells as the primary power source, having secondary batteries for load leveling and eclipse periods.

In the following posts we will see what solutions are available for missions that cannot rely on solar power as a primary source of energy.

Carnival of Space #71 is hosted by Rob at DotAstronomy. Check out the new articles from around the space blogosphere this week!

This post is the first in a series discussing how power is generated onboard spacecrafts.

Credits: NASA

One major component of a spacecraft is the power system. All systems onboard a spacecraft need electricity in order to run. From the early days of space flight, development of this essential system has been a challenge for spacecraft designers.

There are a number of factors that spacecraft designers must take into account: the size, the accessibility, and some operational constraints that can limit the options available. A good example of operational constraints is a spacecraft operating in the Van Allen radiation belts, where radiation exposure can contribute to the rapid degradation of the solar arrays. Other important factors that designers need to consider are the lifetime required by the mission, the orbital parameters, and the attitude control concept employed.

Probably some space geeks (especially science fiction fans) would think of M/AM reactors onboard spacecrafts, but the reality is not as glamorous. Maybe future generations of spacecrafts will use that type of technology, but the present generation is using what some might call primitive technology by comparison.

Credits: NASA

As a general requirement, power systems must control, condition, and process the power received in order to comply with the needs of the systems onboard the spacecraft. The power is received from the primary source, which can be a battery, a solar array, etc. For the duration of the mission, the power system must supply stable and uninterrupted power. If not, the mission is lost.

In the second part of this series, we will take a look at the options available to spacecraft engineers when designing the power system for space missions.

Yes, they do. They really do! One of NASA’s deep space mission probes, New Horizons, is undergoing a check. The mission operators wake the spacecraft out of hibernation once a year. A number of checks are performed: the antennas must be pointed toward Earth, the trajectory must be corrected if needed, and instruments must be calibrated. These checks last more than a usual visit to a doctor… about 50 days. The operators verify the health of the spacecraft, perform maintenance on subsystems and instruments, and gather navigation data.

Credits: NASA

The highlight of the current check was the upload of a new version of the software that runs the spacecraft’s Command and Data Handling system. The brain transplant, as it was called, was a success. The mission team at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, sent the updates through NASA’s Deep Space Network (DSN) to the spacecraft. Two more updates are to be sent for both the Autonomy and Guidance and Control systems.

All commands that are sent to the spacecraft must pass a rigorous development and review process. After the command sequences are tested on the ground, the mission operations team will send them from the New Horizons Mission Operations Center at APL using the DSN, which is operated and managed by NASA’s Jet Propulsion Laboratory.

Credits: NASA

The New Horizons spacecraft was launched on January 19th, 2006 on top of an Atlas V rocket from Cape Canaveral Air Force Station, Florida.

The trajectory chosen for the probe is not complicated, as the probe is flying to Pluto using just one gravity boost from Jupiter. The journey consists of 5 segments: the early cruise, the Jupiter encounter, the interplanetary cruise, the Pluto-Charon encounter, and the Kuiper Belt.

During the early cruise segment of the voyage, spacecraft and instrument checkouts, instrument calibrations, and trajectory corrections were performed. Rehearsals for the Jupiter encounter were also conducted.

During the second segment of the voyage, the closest approach to Jupiter occurred on February 28th, 2007.

Credits: JHUAPL / SwRI

The third segment of the voyage consists mainly of spacecraft and instrument checkouts, trajectory corrections, instrument calibrations, and Pluto encounter rehearsals. This part of the voyage lasts for 8 years and is the current segment of the mission.

The Pluto-Charon encounter is planned for July 14th, 2015.

In the Kuiper Belt, plans are for one or two encounters with Kuiper Belt Objects (KBOs). These objects would be in the 40 to 90 kilometer size range and New Horizons would acquire the same data it collected during the Pluto-Charon encounter and send it back to Earth for analysis.

Credits: JHUAPL / SwRI

New Horizons is a small spacecraft. It weighs 478 kilograms in total, of which 77 kilograms is the hydrazine fuel, and 30 kilograms the scientific instruments. It measures 0.7×2.1×2.7 meters.

For communication with Earth, the spacecraft is using a 2.1 meter high-gain antenna. The data transfer rate is 38 kilobits per second at Jupiter, and 0.6 to 1.2 kilobits per second at Pluto. The data gathered during the encounter with Pluto will take 9 months to transmit back to Earth.

The scientific payload of the spacecraft draws less than 28 Watts of power. The mission uses a radioisotope thermoelectric generator (RTG) for power generation. The RTG contains 11 kilograms of plutonium dioxide. At the start of the mission, the RTG provided 240 Watts of energy at 30 Volts. Due to the decay of the plutonium, the power output decreases during the mission, and by the time of the Pluto encounter the RTG will only produce about 200 Watts.

The scientific instruments that were selected meet the mission’s goals. NASA set out a list of things it wanted to know about Pluto: the composition and behavior of the atmosphere, the appearance of the surface, the geological structures on the surface of Pluto, etc. The scientific payload contains seven instruments.

Credits: NASA

Ralph is a visible and infrared imager/spectrometer. It will obtain high-resolution color maps and surface composition maps of the surfaces of Pluto and Charon.

Alice is an ultraviolet imaging spectrometer. It will be used to analyze the composition and the structure of Pluto’s atmosphere and to look for atmospheres around Charon and Kuiper Belt Objects (KBOs).

REX is the Radio Science Experiment. It is a passive radiometer that measures atmospheric composition and temperature by using what is called an occultation technique: after passing Pluto, the spacecraft will point its antenna back to Earth and record the transmissions sent by the NASA’s DSN. The alterations of the transmissions caused by Pluto’s atmosphere will be recorded and sent back to Earth for analysis. REX will also be used to measure weak radio emissions from Pluto itself.

LORRI stands for Long Range Reconnaissance Imager. It is a telescopic camera and it will be used to obtain encounter data at long distances, to map Pluto’s far side and to provide high-resolution geologic data. LORRI will take images having 100-meter resolution.

SWAP, the solar wind and plasma spectrometer, stands for Solar Wind Around Pluto. It will measure the atmospheric escape rate and it will observe Pluto’s interaction with solar wind, determining whether Pluto has a magnetosphere or not.

Credits: NASA / JHUAPL

PEPSSI, Pluto Energetic Particle Spectrometer Science Investigation, is an energetic particle spectrometer used to measure the composition and density of plasma (ions) escaping from Pluto’s atmosphere.

SDC is the Student Dust Counter. It is the first scientific instrument built by students mounted on a space probe. It measures the space dust impacting the spacecraft during the voyage across the solar system, recording the count and the size of dust particles. It was built primarily by students from the University of Colorado in Boulder, with supervision from scientists.

If you want to know the present location of the spacecraft, there is a dedicated page on APL that you can visit.

For more information on the New Horizons Mission you can read the New Horizons Missions Guides document on the APL website.

The New Horizons Mission also has a page on Twitter.

Welcome to The OrbitalHub – the place where space exploration, science, and engineering meet. My name is DJ and I will be your host for this week’s Carnival. This is not only my first time participating in the Carnival, but also my first time hosting it. I hope you will enjoy reading this week’s entries.

Stuart Atkinson at the Cumbrian Sky points out that ESA marked a successful and historic day by beginning to involve the public more in their missions. He reminds us about some past missions that ESA was very reluctant to share with the general public.

Credits: NASA

On October 10, 2008, the Space Shuttle Atlantis will lift off on a fourth service mission to the Hubble Space Telescope. This sky veteran has served astronomers over the past (almost) two decades. On Astronomy at the CCSSC Rosa Williams explains why this mission is important and presents the upgrades that Hubble will undergo.

Space Shuttle flights may end in 2010. Alpha Magnetic Spectrometer, an ambitious cosmic ray experiment, is completed and sitting on the ground without a ride to the Space Station. The AMS mission may coincide with Shuttle retirement. Read The Last Flight at A Babe in the Universe to find out how scientists and the US Congress strongly support an extra mission for AMS. One controversial plan would deliver AMS and retire an Orbiter in space. The AMS mission would be a dramatic end to the Shuttle era.

On Kentucky Space, we can see how The Space Systems Design Studio at Cornell has been studying some superconducting technologies that might enable the building of modular spacecrafts.

Alexander DeClama, on Potentia Tenebras Repellendi, outlines more arguments on why space exploration is justified. Many byproducts of the space industry have migrated into healthcare and other industries over the years, bringing with them increased quality and reliability.

Centauri Dreams, in Cepheid Variables: A Galactic Internet?, looks at a recent paper that speculates on how a super-civilization might be able to modulate the extremely useful (and highly visible) Cepheid variable stars to encode a signal, for broadcast as one type of interstellar beacon. Intriguingly, if such a long-shot scenario turned out to be true, we might actually have data that could confirm it in existing records about Cepheid variables. The authors suggest how we might parse that data, and how future observations could help with such studies.

Ian Musgrave at Astroblog presents an animation of a cloud floating high above the Martian surface. He used Mars Express VMC camera images that ESA has released to the general public for analysis and processing.

Inspired by an article on Centauri Dreams, Music of the Spheres does some virtual space sailing with the help of the Orbiter space flight simulator and a solar sail add-on.

On The Planetary Society Weblog, Emily Lakdawalla covers a hot topic this week in the blogosphere: the encounter of ESA’s Rosetta with asteroid Steins.

David Portree of Altair VI describes the challenges that astronauts must face living and working in microgravity and an ambitious plan for the settlement of Mars in Delivering settlers to Mars (1995). The plan was initially published in the August 1995 issue of the Journal of the British Interplanetary Society by NASA Ames Research Center engineer Gary Allen.

Since the landing on Mars, the Phoenix lander has developed some odd little clumps on one of its legs, leading to speculations about their origin. Read about them on The Meridiani Journal in What is growing on Phoenix?

Even if space is a very harsh environment, it has been demonstrated that the water bears, a sea-monkey-like creature, can survive in the hard vacuum of space. Read all about it on Visual Astronomy in the article that Sean Welton has submitted for this week’s Carnival: Bears in Space?

Any old school astronomy geeks around here? Steinn Sigurdsson presents an illustration of Homeric Epicycles on Dynamics of Cats.

Credits: NASA/Pat Rawlings

Arthur C. Clarke’s vision of the future seems to be closer to reality as advances are made in separating carbon nanotubes. Read Brian Wang’s post Advance in separating carbon nanotubes brings space elevators a step closer at Next Big Future. This is a significant step towards building a space elevator and towards wider scale use of carbon nanotubes for other applications.

The future in space (and on Earth) of the next 20 years is so bright, you’ll probably need shades… Bruce Cordell of 21st Century Waves explains why in the post Why the World is Not Going to End.

It seems like the LHC (Large Hadron Collider) has an abort button! Thankfully, LHC physicists have a sense of humor about all of this doomsday mumbo-jumbo. Dave Mosher of Space Disco posted a picture of the ‘device’ in The LHC’s Abort Button.

At One Astronomer’s Noise, Nicole Gugliucci tells us about the successful attempt to resolve the super massive black hole at the center of our galaxy. Astronomers used what is called 1.3mm VLBI (Very Long Baseline Interferometry). VLBI is a technique that allows you to create a giant virtual telescope by linking multiple telescopes across long distances.

Measuring the positron emissions of the giant black hole at the center of the universe is quite a challenge. Ethan Siegel, at Starts With A Bang!, presents measurements taken by a detector in the gamma-ray domain and why these measurements are up for debate.

On Cosmic Ray, Ray Villard explores the possibility that the satellites of a Jovian-like planet orbiting around Epsilon Eridani, a star only 10 light-years away from our solar system, could harbor the seeds of life.

Credits: MOST Science Team

David Gamey, from Mang’s Bat Page, posted three articles about MOST (Microvariability and Oscillations of Stars), the suitcase sized microsatellite designed to probe stars and extra solar planets by measuring tiny light variations undetectable from Earth. By using a computer-controlled telescope, an astronomer from Toronto was able to catch MOST on camera. The MOST also started to offer its services to the public: Canadian amateur astronomers can win time on MOST. Even though it is a small telescope, MOST can be used to detect asteroids in an exo planetary system.

If you are an amateur astronomer, Alan Dyer at What’s Up Astronomy can show you how to catch on camera a cosmic flasher. Under the right conditions, the sunlight, reflected by the solar panels of communication satellites, can be observed from Earth.

The Earth is not left out this week. Phil Plait aka The Bad Astronomer, at Bad Astronomy, presents Ten things you don’t know about the Earth. I do not want to spoil the pleasure of reading the post, but I have to mention one of them: there is a measurable effect due to the centrifugal forces caused by the spinning motion of the Earth. The Earth’s diameter measured across the Equator is ~42km bigger than the diameter measured between the poles!

That’s it for this week’s Carnival! Thanks to everyone who submitted an entry. I enjoyed reading all of the posts and getting to know some members of the community. For more details on the Carnival of Space and past editions, you can check out the Carnival page at Universe Today. Many thanks to Fraser Cain at Universe Today for inviting me to host this Carnival.