Bullseye: Amazing SpaceX Images Highlight Perfect Falcon 9 Landing

A SpaceX Falcon 9 rocket just before landing on the drone ship ‘Just Read the Instructions’ in the Pacific Ocean, on January 14, 2017 following the launch of 10 Iridium NEXT satellites into orbit. Credit: SpaceX.

SpaceX was able to celebrate a successful return to flight this week with a picture-perfect launch of the Falcon 9 rocket on January 14, 2017 that successfully delivered a fleet of ten advanced Iridium NEXT mobile voice and data relay satellites to orbit. But the icing on the cake was the dead-center landing and recovery of the Falcon 9 booster on their drone barge (named “Just Read The Instructions”) in the Pacific Ocean, off the west coast of California.

SpaceX released some images from the landing that are absolutely stunning, like this one, below:

A stunning view of the Falcon 9 rocket just before landing on a barge in the Pacific Ocean, on January 14, 2017 following the launch of 10 Iridium NEXT satellites into orbit. Credit: SpaceX.

The Falcon 9 launched from Space Launch Complex 4E on Vandenberg Air Force Base in California, and the main goal of the mission was to deploy the payload of the first ten Iridium Next communication satellites to low Earth orbit. Iridium plans to eventually have a fleet of 81 such satellites.

It was the first launch for the commercial company since the September 1, 2016 explosion on the launchpad at Cape Canaveral Air Force Station in Florida during a routine launchpad test. The explosion destroyed the Falcon 9 rocket and the payload of the Amos-6 communications satellite, which had an estimated value of $200 million. The explosion was traced back to a failure of a high-pressure helium vessel inside the Falcon 9’s second-stage liquid-oxygen tank.

Enjoy more images and video from the landing below:

Another view of the SpaceX Falcon 9 booster after landing on a barge in the Pacific Ocean on January 14, 2017. Credit: SpaceX.
The Falcon 9 booster sitting successfully on the barge after landing. Credit: SpaceX.

Here’s the full webcast of both the launch and landing:

You can see all of SpaceX’s latest images on their Flickr stream.

Here’s a High-Res Look at Philae’s Landing Spot

Mosaic of OSIRIS images of landing site "J" on Comet 67P/CG. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The long-awaited deployment of the Philae lander, currently “piggybacked” aboard ESA’s Rosetta spacecraft orbiting the nucleus of Comet 67P/Churyumov-Gerasimenko, will occur in less than a month and we now have our best look yet at the area now green-lighted for touchdown. The picture above, made from two images acquired by Rosetta’s OSIRIS imaging instrument, shows a 500-meter circle centered on “Site J,” a spot on the comet’s “head” carefully chosen by mission scientists as the best place in which Philae should land, explore, and ultimately travel around the Sun for the rest of its days. And as of today, it’s a GO!

Site J was selected from among five other possible sites and was chosen because of the relative safety of its surface, its accessibility to consistent solar illumination, and the scientific and observational data it can make available to Philae’s suite of onboard instruments.

“None of the candidate landing sites met all of the operational criteria at the 100% level, but Site J is clearly the best solution,” said Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center.

Illustration of the Rosetta Missions Philae lander on final approach to a comet surface. The date is now set for landing, November 12. (Photo: ESA)
Illustration of the Rosetta Missions Philae lander on final approach to a comet surface. The date is now set for landing, November 12. (Photo: ESA)

Read more: Comet’s Head Selected as Landing Site for Rosetta’s Historic Philae Lander

The mosaic above comprises two images taken by Rosetta’s OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) narrow-angle camera on Sept. 14 from a distance of about 30 km (18.6 miles). Image scale is 0.5 m/pixel.

As Comet 67P/CG continues toward perihelion its outgassing and sublimation jetting will undoubtedly increase, and Philae will be getting a front-row seat to the action.

“Site J is just 500-600 meters away from some pits and an area of comet outgassing activity,” said Holger Sierks, principal investigator for Rosetta’s OSIRIS camera from the Max Planck Institute for Solar System Research in Gottingen, Germany. “They will become more active as we get closer to the Sun.”

Watch “Landing on a Comet: the Trailer”

After completing a series of “Go/No-go” decisions by Rosetta’s flight dynamics team, Philae’s separation from Rosetta will occur on Nov. 12 at 08:35 GMT. It will land about seven hours later at around 15:30 GMT. Because of the distance to the comet and spacecraft — about 509 million km — confirmation of a successful touchdown won’t be received on Earth until 28 minutes and 20 seconds later. (And you thought Curiosity’s “seven minutes of terror” was nerve-wracking!)

Read more here on ESA’s Rosetta blog.

Landing on a Comet: The Trailer

Artist's impression of the 100-kg Philae lander (screenshot) Credit: ESA/DLR

In less than a month, on November 12, 2014, the 100-kg Philae lander will separate from ESA’s Rosetta spacecraft and descend several kilometers down to the dark, dusty and frozen surface of Comet 67P/Churyumov-Gerasimenko, its three spindly legs and rocket-powered harpoon all that will keep it from crashing or bouncing hopelessly back out into space. It will be the culmination of a decade-long voyage across the inner Solar System, a testament to human ingenuity and inventiveness and a shining example of the incredible things we can achieve through collaboration. But first, Philae has to get there… it has to touch down safely and successfully become, as designed, the first human-made object to soft-land on the nucleus of a comet. How will the little spacecraft pull off such a daring maneuver around a tumbling chunk of icy rubble traveling over 18 km/s nearly 509 million km away? The German Aerospace Center (DLR) has released a “trailer” for the event, worthy of the best sci-fi film. Check it out below.

Want to see more? Of course you do. Keep an eye out for the 11-minute short film “Landing on a Comet – The Rosetta Mission” to be released soon on YouTube here, and follow the latest news from the Rosetta mission here (and here on Universe Today, too!)

“The reason we’re at this comet is for science, no other reason. We’re doing this to get the best science. To characterize this comet has never been done before.”

Original Material: DLR (CC-BY 3.0)
Footage: ESA
Music: Omega by TimMcMorris

Source: DLR

ESA’s Rosetta Mission sets November 12th as the Landing Date for Philae

Illustration of the Rosetta Missions Philae lander on final approach to a comet surface. (Photo: ESA)

ESA Rosetta mission planners have selected November 12th, one day later than initially planned, for the historic landing of Philae on a comet’s surface. The landing on 67P/Churyumov-Gerasimenko will be especially challenging for the washing machine-sized lander. While mission scientists consider their choice of comet for the mission to be an incredibly good one for scientific investigation and discovery, the irregular shape and rugged terrain also make for a risky landing. The whole landing is not unlike the challenge one faces in shooting a moving target in a carnival arcade game; however, this moving target is 20 kilometers below and it is also rotating.

At  8:35 GMT (3:35 AM EST), the landing sequence will begin with release of Philae by Rosetta at an altitude of 20 kilometers above the comet. The expected time of touchdown is seven hours later – 15:35 GMT (10:35 AM EST). During the descent, Philae’s ROLIS camera will take a continuous series of photos. The comet will complete more than half a rotation during the descent; comet P67’s rotation rate is 12.4 hours. The landing site will actually be on the opposite side of the comet when Philae is released and will rotate around, and if all goes as planned, meet Philae at landing site J.

Before November 12th, mission planners will maintain the option of landing at Site C. If the alternate site is chosen, the descent will begin at 13:04 GMT also on November 12 but from an altitude of 12.5 kilometers, a 4 hour descent time.

NAVCAM image of the comet on 21 September, which includes a view of primary landing site J. Click for more details and link to context image. (Credits: ESA/Rosetta/NAVCAM)
NAVCAM image of the comet on 21 September, which includes a view of primary landing site J. Click for more details and link to context image. (Credits: ESA/Rosetta/NAVCAM)

Rosetta will eject Philae with an initial velocity of approximately 2 1/2  kilometers per hour. Because the comet is so small, its gravity will add little additional speed to Philae as it falls to the surface. Philae is essentially on a ballistic trajectory and does not have any means to adjust its path.

The actions taken by Philae’s onboard computer begin only seconds from touchdown. It has a landing propulsion system but unlike conventional systems that slow down the vehicle for soft landing, Philae’s is designed to push the lander snugly onto the comet surface. There is no guarantee that Philae will land on a flat horizontal surface. A slope is probably more likely and the rocket will force the small lander’s three legs onto the slope.

A model of the comet P67/Churyumov-Gerasimenko created using images from the Rosetta OSIRIS narrow field camera. (Credit: ESA)
A model of the comet P67/Churyumov-Gerasimenko created using images from the Rosetta OSIRIS narrow field camera. Mouse click on the image to start the animated GIF. (Credit: ESA)

Landing harpoons will be fired that are attached to cables that will be pulled in to also help Philae return upright and attach to the surface. Philae could actually bounce up or topple over if the rocket system and harpoons fail to do their job.

The Philae Lander anchoring harpoon with the integrated MUPUS-accelerometer and temperature sensor. (Credit: "Philae Lander Fact Sheet", ESA)
The Philae Lander anchoring harpoon with the integrated MUPUS-accelerometer and temperature sensor. (Credit: “Philae Lander Fact Sheet”, ESA)

However, under each of the three foot pads, there are ice screws that will attempt to drill and secure Philae to the surface. This will depend on the harpoons and/or rockets functioning as planned, otherwise the action of the drills could experience resistance from hard ground and simply push the lander up rather than secure it down. Philae also has a on-board gyro to maintain its attitude during descent, and an impact dampener on the neck of the vehicle which attaches the main body to the landing struts.

Ten landing sites were picked, then down-selected to five, and then finally on September 15th, they selected Site J on the head of the smaller lobe – the head of the rubber duck, with site C as a backup. Uncertainty in the release and the trajectory of the descent to the comet’s surface means that the planners needed to find a square kilometer area for landing. But comet 67P/Churyumov-Gerasimenko simply offered no site with that much flat area clear of cliffs and boulders. Philae will be released to land at Site J which offers some smooth terrain but only about a quarter of the area needed to assure a safe landing. Philae could end up landing on the edge of a cliff or atop a large boulder and topple over.

A 'color' view of Comet 67P, from a September 24, 2014 NavCam image. Credits: ESA/Rosetta/NavCam - Processing by Elisabetta Bonora & Marco Faccin.
A ‘color’ view of Comet 67P, from a September 24, 2014 NavCam image. Credits: ESA/Rosetta/NavCam – Processing by Elisabetta Bonora & Marco Faccin.

The Rosetta ground control team will have no means of controlling and adjusting Philae during the descent. This is how it had to be because the light travel time for telecommunications from the spacecraft to Earth does not permit real-time control. The execution time and the command sequence will be delivered to Rosetta days before the November 12th landing. And ground control must maneuver Rosetta with Philae still attached to an exact point in space where the release of Philae must take place. Any inaccuracy in the initial release point will be translated all the way down to the surface and Philae would land some undesired distance away from Site J. However, ground controllers have a month and a half to practice simulations of the landing many times over with a model of the comet’s nucleus. With practice and more observational data between now and the landing, the initial conditions and model of the comet in the computer simulation will improve and raise the likelihood of a close landing to Site J.

Previous Universe Today articles on Rosetta’s Philae:

How do you land on a comet? Very carefully.

Rosetta’s Philae Lander: A Swiss Army Knife of Scientific Instruments

Comet’s Head Selected as Landing Site for Rosetta’s Historic Philae Lander

Rosetta’s Philae Lander: A Swiss Army Knife of Scientific Instruments

Rosetta's Philae lander is Like a modern-day Swiss Army Knife, now prepared for a November 11th dispatch to a comet's surface.

When traveling to far off lands, one packs carefully. What you carry must be comprehensive but not so much that it is a burden. And once you arrive, you must be prepared to do something extraordinary to make the long journey worthwhile.

The previous Universe Today article “How do you land on a Comet?” described Philae’s landing technique on comet 67P/Churyumov-Gerasimenko. But what will the lander do once it arrives and gets settled in its new surroundings? As Henry David Thoreau said, “It is not worthwhile to go around the world to count the cats in Zanzibar.” So it is with the Rosetta lander Philae. With the stage set – a landing site chosen and landing date of November 11th, the Philae lander is equipped with a carefully thought-out set of scientific instruments. Comprehensive and compact, Philae is a like a Swiss Army knife of tools to undertake the first on-site (in-situ) examination of a comet.

Now, consider the scientific instruments on Philae which were selected about 15 years ago. Just like any good traveler, budgets had to be set which functioned as constraints on the instrument selection that could be packed and carried along on the journey. There was a maximum weight, maximum volume, and power. The final mass of Philae is 100 kg (220 lbs). Its volume is 1 × 1 × 0.8 meters (3.3 × 3.3 × 2.6 ft)  about the size of a four burner oven-range. However, Philae must function on a small amount of stored energy upon arrival: 1000 Watt-Hours (equivalent of a 100 watt bulb running for 10 hours). Once that power is drained, it will produce a maximum of 8 watts of electricity from Solar panels to be stored in a 130 Watt-Hour battery.

Side view schematics of the inner structure of the lander compartment showing the location of COSAC and PTOLEMY systems, the CONSERT antennas, the SESAME dust sensor and various ÇIVA cameras (Credits: "Capabilities of Philae, the Rosetta Lander, J. Biele, S. Ulamec, September 2007)
Side view schematics of the inner structure of the lander compartment showing the location of COSAC, PTOLEMY, the CONSERT antennas, the SESAME dust sensor and ÇIVA cameras. Philae is about the size of a dishwasher or four burner oven. (Credits: “Capabilities of Philae, the Rosetta Lander, J. Biele, S. Ulamec, September 2007)

Without any assurance that they would land fortuitously and produce more power, the Philae designers provided a high capacity battery that is charged, one time only, by the primary spacecraft solar arrays (64 sq meters) before the descent to the comet. With an initial science command sequence on-board Philae and the battery power stored from Rosetta, Philae will not waste any time to begin analysis — not unlike a forensic analysis — to do a “dissection” of a comet. Thereafter, they utilize the smaller battery which will take at least 16 hours to recharge but will permit Philae to study 67P/Churyumov-Gerasimenko for potentially months.

There are 10 science instrument packages on the Philae lander. The instruments use absorbed, scattered, and emitted light, electrical conductivity, magnetism, heat, and even acoustics to assay the properties of the comet. Those properties include the surface structure (the morphology and chemical makeup of surface material), interior structure of P67, and the magnetic field and plasmas (ionized gases) above the surface. Additionally, Philae has an arm for one instrument and the Philae main body can be rotated 360 degrees around its Z-axis. The post which supports Philae and includes a impact dampener.

CIVA and ROLIS imaging systems. CIVA represents three cameras which share some hardware with ROLIS. CIVA-P (Panoramic) is seven identical cameras, distributed around the Philae body but with two functioning in tandem for stereo imaging. Each has a 60 degree field of view and uses as 1024×1024 CCD detector. As most people can recall, digital cameras have advanced quickly in the last 15 years. Philae’s imagers were designed in the late 1990s, near state-of-the-art, but today they are surpassed, at least in number of pixels, by most smartphones. However, besides hardware, image processing in software has advanced as well and the images may be enhanced to double their resolution.

CIVA-P will have the immediate task, as part of the initial autonomous command sequence, of surveying the complete landing site. It is critical to the deployment of other instruments. It will also utilize the Z-axis rotation of the Philae body to survey. CIVA-M/V is a microscopic 3-color imager (7 micron resolution) and CIVA-M/I is a near infra-red spectrometer (wavelength range of 1 to 4 microns) that will inspect each of the samples that is delivered to the COSAC & PTOLEMY ovens before the samples are heated.

The CIVA micro-camera. Mass: less than 100 grams, Power: less than 2 Watts, Minimum Operating Temperature: -120C (Credit:ESA, Philae Lander Fact Sheet)
The CIVA micro-camera. Mass: less than 100 grams, Power: less than 2 Watts, Minimum Operating Temperature: -120C (Credit:ESA, Philae Lander Fact Sheet)

ROLIS is a single camera, also with a 1024×1024 CCD detector, with the primary role of surveying the landing site during the descent phase. The camera is fixed and downward pointing with an f/5 (f-ratio) focus adjustable lens with a 57 degree field of view. During descent it is set to infinity and will take images every 5 seconds. Its electronics will compress the data to minimize the total data that must be stored and transmitted to Rosetta. Focus will adjust just prior to touchdown but thereafter, the camera functions in macro mode to spectroscopically survey the comet immediately underneath Philae. Rotation of the Philae body will create a “working circle” for ROLIS.

The multi-role design of ROLIS clearly shows how scientists and engineers worked together to overall reduce weight, volume, and power consumption, and make Philae possible and, together with Rosetta, fit within payload limits of the launch vehicle, power limitations of the solar cells and batteries, limitations of the command and data system and radio transmitters.

Philae's APXS - Alpha Proton X-Ray Spectrometer (Credit: Inst. for Inorganic Chemistry & Analytical Chemistry, Max-Planck Institute for Chemistry)
Philae’s APXS – Alpha Proton X-Ray Spectrometer (Credit: Inst. for Inorganic Chemistry & Analytical Chemistry, Max-Planck Institute for Chemistry)

APXS. This is a Alpha Proton X-ray Spectrometer. This is a near must-have instrument of the space scientist’s Swiss Army Knife. APXS spectrometers have become a common fixture on all Mars Rover missions and Philae’s is an upgraded version of Mars Pathfinder’s. The legacy of the APXS design is the early experiments by Ernest Rutherford and others that led to discovering the structure of the atom and the quantum nature of light and matter.

This instrument has a small source of Alpha particle emission (Curium 244) essential to its operation. The principles of Rutherford Back-scattering of Alpha particles is used to detect the presence of lighter elements such as Hydrogen or Beryllium (those close to an Alpha particle in mass, a Helium nucleus). The mass of such lighter elemental particles will absorb a measurable amount of energy from the Alpha particle during an elastic collision; as happens in Rutherford back-scattering near 180 degrees. However, some Alpha particles are absorbed rather than reflected by the nuclei of the material. Absorption of an Alpha particle causes emission of a proton with a measurable kinetic energy that is also unique to the elemental particle from which it came (in the cometary material); this is used to detect heavier elements such as magnesium or sulfur. Lastly, inner shell electrons in the material of interest can be expelled by Alpha particles. When electrons from outer shells replace these lost electrons, they emit an X-Ray of specific energy (quantum) that is unique to that elementary particle; thus, heavier elements such as Iron or Nickel are detectable. APXS is the embodiment of early 20th Century Particles Physics.

CONSERT. COmet Nucleus Sounding Experiment by Radio wave Transmission, as the name suggests, will transmit radio waves into the comet’s nucleus. The Rosetta orbiter transmits 90 MHz radio waves and simultaneously Philae stands on the surface to receive with the comet residing between them. Consequently, the time of travel through the comet and the remaining energy of the radio waves is a signature of the material through which it propagated. Many radio transmissions and receptions by CONSERT through a multitude of angles will be required to determine the interior structure of the comet. It is similar to how one might sense the shape of a shadowy object standing in front of you by panning one’s head left and right to watch how the silhouette changes; altogether your brain perceives the shape of the object. With CONSERT data, a complex deconvolution process using computers is necessary. The precision to which the comet’s interior is known improves with more measurements.

MUPUS. Multi-Purpose Sensor for Surface and Subsurface Science is a suite of detectors for measuring the energy balance, thermal and mechanical properties of the comet’s surface and subsurface down to a depth of 30 cm (1 foot).  There are three major parts to MUPUS. There is the PEN which is the penetrator tube. PEN is attached to a hammering arm that extends up to 1.2 meters from the body. It  deploys with sufficient downward force to penetrate and bury PEN below the surface; multiple hammer strokes are possible. At the tip, or anchor, of PEN (the penetrator tube) is an accelerometer and standard PT100 (Platinum Resistance Thermometer). Together, the anchor sensors will determine the hardness profile at the landing site and the thermal diffusivity at the final depth [ref]. As it penetrates the surfaces, more or less deceleration indicates harder or softer material. The PEN includes an array of  16 thermal detectors along its length to measure subsurface temperatures and thermal conductivity. The PEN also has a heat source to transmit heat to the cometary material and measure its thermal dynamics. With the heat source off, detectors in PEN will monitor the temperature and energy balance of the comet as it approaches the Sun and heats up. The second part is the MUPUS TM,  a radiometer atop the PEN which will measure thermal dynamics of the surface. TM consists of four thermopile sensors with optical filters to cover a wavelength range from 6-25 µm.

SD2 Sample Drill and Distribution device will penetrate the surface and subsurface to a depth of 20 cm. Each retrieved sample will be a few cubic millimeters in volume and distributed to 26  ovens mounted on a carousel. The ovens heat the sample which creates a gas that is delivered to the gas chromatographs and mass spectrometers that are COSAC and PTOLEMY. Observations and analysis of APXS and ROLIS data will be used to determine the sampling locations all of which will be on a “working circle” from the rotation of Philae’s body about its Z-axis.

COSAC Cometary Sampling and Composition experiment. The first gas chromatograph (GC) I saw was in a college lab and was being used by the lab manager for forensic tests supporting the local police department. The intent of Philae is nothing less than to perform forensic tests on a comet hundred of million of miles from Earth. Philae is effectively Sherlock Holmes’ spy glass and Sherlock is all the researchers back on Earth. The COSAC gas chromatograph includes a mass spectrometer and will measure the quantities of elements and molecules, particularly complex organic molecules, making up comet material. While that first lab GC I saw was closer to the size of Philae, the two GCs in Philae are about the size of shoe boxes.

Philae's two Gas Chromatograph (GC). Left: COSAC, integrated into Philae, Right: PTOLEMY on an engineering lab. (Credit: ESA)
Philae’s two Gas Chromatographs (GC). Left: COSAC, integrated into Philae, Right: PTOLEMY in an engineering lab. (Credit: ESA)

PTOLEMY. An Evolved Gas Analyzer [ref], a different type of gas chromatograph. The purpose of Ptolemy is to measure the quantities of specific isotopes to derive the isotopic ratios, for example, 2 parts isotope C12 to one part C13. By definition, isotopes of an element have the same number of protons but different numbers of neutrons in their nuclei. One example is the 3 isotopes of Carbon, C12, C13 and C14; the numbers being the number of neutrons. Some isotopes are stable while others can be unstable – radioactive and decay into stable forms of the same element or into other elements. What is of interest to Ptolemy investigators is the ratio of stable isotopes (natural and not those affected by, or that result from, radioactive decay) for the elements H, C, N, O and S, but particularly Carbon. The ratios will be telltale indicators of where and how comets are created. Until now, spectroscopic measurements of comets to determine isotopic ratios have been from a distance and the accuracy has been inadequate for drawing firm conclusions about the origin of comets and how comets are linked to the creation of planets and the evolution of the Solar Nebula, the birthplace of our planetary system surrounding the Sun, our star. An evolved gas analyzer will heat up a sample (~1000 C) to transform the materials into a gaseous state which a spectrometer can very accurately measure quantities. A similar instrument, TEGA (Thermal Evolved Gas Analyzer) was an instrument on Mars Phoenix lander.

SESAME Surface Electrical Sounding and Acoustic Monitoring Experiment This instrument involves three unique detectors. The first is the SESAME/CASSE, the acoustic detector. Each landing foot of Philae has acoustic emitters and receivers. Each of the legs will take turns transmitting acoustic waves (100 Hertz to KiloHertz range) into the comet which the sensors of the other legs will measure. How that wave is attenuated, that is, weakened and transformed, by the cometary material it passes through, can be used along with other cometary properties gained from Philae instruments, to determine daily and seasonal variations in the comet’s structure to a depth of about 2 meters. Also, in a passive (listening) mode, CASSE will monitor sound waves from creaks, groans inside the comet caused potentially by stresses from Solar heating and venting gases.

Next is the SESAME/PP detector – the Permittivity Probe. Permittivity is the measure of the resistance a material has to electric fields. SESAME/PP will deliver an oscillating (sine wave) electric field into the comet. Philae’s feet carry the receivers – electrodes and AC sine generators to emit the electric field. The resistance of the cometary material to about a 2 meter depth is thus measured providing another essential property of the comet – the permittivity.

Philae SESAME/DIM, Dust Impact Monitor. The monitor can measure particle size and velocity. Later as comet P67's activity rises, it can continue to return total particle flux. (Credit: ESA)
Philae SESAME/DIM, Dust Impact Monitor. The monitor can measure particle size and velocity. Later as comet P67’s activity rises, it can continue to return total particle flux. (Credit: ESA)

The third detector is called SESAME/DIM. This is the comet dust counter. There were several references used to compile these instrument descriptions. For this instrument, there is, what I would call, a beautiful description which I will simply quote here with reference. “The Dust Impact Monitor (DIM) cube on top of the Lander balcony is a dust sensor with three active orthogonal (50 × 16) mm piezo sensors. From the measurement of the transient peak voltage and half contact duration, velocities and radii of impacting dust particles can be calculated. Particles with radii from about 0.5 µm to 3 mm and velocities from 0.025–0.25 m/s can be measured. If the background noise is very high, or the rate and/or the amplitudes of the burst signal are too high, the system automatically switches to the so called Average Continuous mode; i.e., only the average signal will be obtained, giving a measure of the dust flux.” [ref]

ROMAP Rosetta Lander Magnetometer and Plasma detector also includes a third detector, a pressure sensor. Several spacecraft have flown by comets and an intrinsic magnetic field, one created by the comet’s nucleus (the main body) has never been detected. If an intrinsic magnetic field exists, it is likely to be very weak and landing on the surface would be necessary. Finding one would be extraordinary and would turn theories regarding comets on their heads. Low and behold Philae has a fluxgate magnetometer.

Philae ROMAP, Tri-Axial Fluxgate magnetometer and Plasma Monitor (Credit: ESA/MPS)
Philae ROMAP, Tri-Axial Fluxgate Magnetometer and Plasma Monitor (Credit: ESA/MPS)

The Earth’s magnetic (B) field surrounding us is measured in the 10s of thousands of nano-Teslas (SI unit, billionth of a Tesla). Beyond Earth’s field, the planets, asteroids, and comets are all immersed in the Sun’s magnetic field which, near the Earth, is measured in single digits, 5 to 10 nano-Tesla. Philae’s detector has a range of +/- 2000 nanoTesla; a just in case range but one readily offered by fluxgates. It has a sensitivity of 1/100th of a nanoTesla. So, ESA and Rosetta came prepared. The magnetometer can detect a very minute field if it’s there. Now let’s consider the Plasma detector.

Much of the dynamics of the Universe involves the interaction of plasma – ionized gases (generally missing one or more electrons thus carrying a positive electric charge) with magnetic fields. Comets also involve such interactions and Philae carries a plasma detector to measure the energy, density and direction of electrons and of positively charged ions. Active comets are releasing essentially a neutral gas into space plus small solid (dust) particles. The Sun’s ultraviolet radiation partially ionizes the cometary gas of the comet’s tail, that is, creates a plasma. At some distance from the comet nucleus depending on how hot and dense that plasma is, there is a standoff between the Sun’s magnetic field and the plasma of the tail. The Sun’s B field drapes around the comet’s tail kind of like a white sheet draped over a Halloween trick-or-treater but without eye holes.

The structure of an active comet. In early 2015, 67P/Churyumov–Gerasimenko will wake-up. The heat of the Sun will increase gas and dust production which will interact with Solar UV radiation and the Solar Wind. The Sun's magnetic field will be draped around the coma and tail of the comet. (Photo: ESA)
The structure of an active comet. In early 2015, 67P/Churyumov–Gerasimenko will wake up. The heat of the Sun will increase gas and dust production which will interact with Solar UV radiation and the Solar Wind. The Sun’s magnetic field will be draped around the coma and tail of the comet. (Photo: ESA)

So at P67’s surface, Philae’s ROMAP/SPM detector, electrostatic analyzers and a Faraday Cup sensor will measure free electrons and ions in the not so empty space. A “cold” plasma surrounds the comet; SPM will detect ion kinetic energy in the range of 40 to 8000 electron-volts (eV) and electrons from 0.35 eV to 4200 eV. Last but not least, ROMAP includes a pressure sensor which can measure very low pressure – a millionth or a billionth or less than the air pressure we enjoy on Earth. A Penning Vacuum gauge is utilized which ionizes the primarily neutral gas near the surface and measures the current that is generated.

Philae will carry 10 instrument suites to the surface of 67P/Churyumov-Gerasimenko but altogether the ten represent 15 different types of detectors. Some are interdependent, that is, in order to derive certain properties, one needs multiple data sets. Landing Philae on the comet surface will provide the means to measure many properties of a comet for the fist time and others with significantly higher accuracy. Altogether, scientists will come closer to understanding the origins of comets and their contribution to the evolution of the Solar System.

‘Avalanche’ Risk Higher Than Thought For Asteroid Landings: Study

Landing on asteroids will be a risky endeavor, perhaps aggravated by changes in asteroid dust when it's touched. Credit: NASA Near Earth Object Program

Imagine plunking your spacecraft down on an asteroid. The gravity would be small. The surface would be uneven. The space rock might be noticeably spinning, complicating your maneuvering.

Humans have done it with robotic spacecraft before. The first time was in 2001, when NASA made a stunning landing with the NEAR Shoemaker spacecraft on Eros — using a craft that was not even designed to reach the surface. A new study, however, portrays getting close to these space rocks as perhaps even more hazardous than previously thought.

An experiment done aboard a “Vomit-Comet” like airplane, which simulates weightlessness, suggests that dust particles on comets and asteroids may be able to feel changes in their respective positions across far larger distances than on Earth.

“We see examples of force-chains everywhere. When you pick an orange from a pile in a supermarket, some come away easily, but others bring the whole lot crashing down.  Those weight-bearing oranges are part of a force-chain in the pile,” stated Naomi Murdoch, a researcher at the Higher Institute of Aeronautics and Space (Institut Supérieur de l’Aéronautique et de l’Espace) in Toulouse, France.

Naomi Murdoch and Thomas-Louis de Lophem in zero gravity alongside the AstEx experiment. Credit: A. Le Floc’h, ESA
Naomi Murdoch and Thomas-Louis de Lophem in a zero gravity environment aboard a parabolic airplane, alongside the AstEx experiment. Credit: A. Le Floc’h, ESA

“One important aspect of such chains is that they give a granular material a ‘memory’ of forces that they have been exposed to. Reversing the direction of a force can effectively break the chain, making the pile less stable.”

The Asteroid Experiment Parabolic Flight Experiment (AstEx) experiment was designed by Murdoch, Open University’s Ben Rozitis, and several collaborators from The Open University, the Côte d’Azur Observatory and the University of Maryland. It had a cylinder with glass beads inside of it, as well as a rotating drum at the heart.

Stacked photo of the grains in the Asteroid Experiment (AstEx). Credit: AstEx team
Stacked photo of the grains in the Asteroid Experiment (AstEx). Credit: AstEx team

In 2009, when they were postgraduate students, Murdoch and Rozitis took their contraption on board an Airbus A300, which flew parabolas to simulate microgravity while the aircraft falls from its greatest height.

During this time, the inner drum spun up for 10 seconds and then the rotational direction was reversed. What happened was tracked by high-speed cameras. Later, the researchers analyzed the movement of the beads with a particle-tracking program.

The researchers found that particles at the edge of the cylinder (the closest analog to low-gravity environments) moved more than those in similar environments on Earth. Those closer to the center, however, were not as greatly affected.

“A lander touching down on the surface on one side of a small, rubble-pile asteroid could perhaps cause an avalanche on the other side, by long-range transmission of forces through chains  It would, however, depend on the angle and location of the impact, as well as the history of the surface – what kind of memories the regolith holds,” said Murdoch.

Check out more details of the experiment in the June 2013 issue of the Monthly Notices of the Royal Astronomical Society. It’s some interesting food for thought as NASA ponders an asteroid retrieval mission that so far has met with skeptical Congress representatives.

Source: Royal Astronomical Society

Curiosity’s Landing Leftovers

Enhanced-color HiRISE image of impact craters from MSL's ballast weights (NASA/JPL-Caltech)

During its “seven minutes of terror” landing on August 6, 2012, NASA’s Mars Science Laboratory dropped quite a few things down onto the Martian surface: pieces from the cruise stage, a heat shield, a parachute, the entry capsule’s backshell, a sky crane, one carefully-placed rover (obviously) and also eight tungsten masses — weights used for ballast and orientation during the descent process.

Two 75 kilogram (165 lb) blocks were released near the top of the atmosphere and six 25 kg (55 lb) weights a bit farther down, just before the deployment of the parachute. The image above, an enhanced-color image from the HiRISE camera aboard the Mars Reconnaissance Orbiter, shows the impact craters from four of these smaller tungsten masses in high resolution. This is part of a surface scan acquired on Jan. 29, 2013.

These four craters are part of a chain of six from all the 55 kg weights. See below for context:

CLICK TO PLAY - Before-and-after images of the 55 kg-mass landing sites (NASA/JPL/MSSS)
CLICK TO PLAY – Before-and-after images of the 55 kg-mass landing sites (NASA/JPL/MSSS)

Captured by MRO’s Context Camera shortly after the rover landed, the animation above shows the impact site of all six 55 kg masses. These impacted the Martian surface about 12 km (7.5 miles) from the Curiosity rover’s landing site.

A mosaic has been assembled showing potential craters from the larger ballast blocks as well as other, smaller pieces of the cruise stage. Check it out below or download the full 50mb image here.

HiRISE images of MSL's impact craters (NASA/JPL/University of Arizona)
HiRISE images of MSL’s impact craters (NASA/JPL/University of Arizona)

As Alfred McEwen wrote in his article on the University of Arizona’s HiRISE site: “most of the stuff we sent to Mars crashed on the surface–everything except the Curiosity rover.”


Neil Armstrong, First Man on the Moon, Dies at 82

Former NASA astronaut Neil A. Armstrong was born in Wapakoneta, Ohio, on August 5, 1930

Today we mourn the loss of a true hero and icon of a generation, if not an entire century: Neil Alden Armstrong, former NASA astronaut and first person to set foot on the Moon, has passed away due to complications from cardiovascular surgery. Armstrong had recently turned 82 years old on August 5.

His family has issued the following statement:

We are heartbroken to share the news that Neil Armstrong has passed away following complications resulting from cardiovascular procedures.

Neil was our loving husband, father, grandfather, brother and friend.

Neil Armstrong was also a reluctant American hero who always believed he was just doing his job. He served his Nation proudly, as a navy fighter pilot, test pilot, and astronaut. He also found success back home in his native Ohio in business and academia, and became a community leader in Cincinnati.

He remained an advocate of aviation and exploration throughout his life and never lost his boyhood wonder of these pursuits.

As much as Neil cherished his privacy, he always appreciated the expressions of good will from people around the world and from all walks of life.

While we mourn the loss of a very good man, we also celebrate his remarkable life and hope that it serves as an example to young people around the world to work hard to make their dreams come true, to be willing to explore and push the limits, and to selflessly serve a cause greater than themselves.

For those who may ask what they can do to honor Neil, we have a simple request. Honor his example of service, accomplishment and modesty, and the next time you walk outside on a clear night and see the moon smiling down at you, think of Neil Armstrong and give him a wink.

His death was reported at 2:45 p.m. ET.

Armstrong commanded the Apollo 11 spacecraft that landed on the moon on July 20, 1969, and he radioed back to Earth the historic news: “That’s one small step for a man, one giant leap for mankind.”

In a statement issued by the White House, U.S. President Barack Obama said “Today, Neil’s spirit of discovery lives on in all the men and women who have devoted their lives to exploring the unknown – including those who are ensuring that we reach higher and go further in space. That legacy will endure — sparked by a man who taught us the enormous power of one small step.”

Neil Armstrong, along with fellow astronauts Buzz Aldrin, Michael Collins and John Glenn, were honored with the Congressional Gold Medal on November 16, 2011.

Godspeed, Mr. Armstrong. You were — and will always be — a true inspiration to so many. You’ll be missed.

“In my own view, the important achievement of Apollo was a demonstration that humanity is not forever chained to this planet, and our visions go rather further than that, and our opportunities are unlimited.”

— Neil A. Armstrong

Top image: NASA. Inset images: Armstrong leads the crew from the Manned Spacecraft Operations Building to the transfer van on July 16, 1969 and a portrait of Armstrong taken inside the LM after the first lunar EVA. Via the Project Apollo Archive.

The First Photo From The Moon

“That’s one small step for a man, one giant leap for mankind.” After speaking these historic words at 10:56 EDT on July 20, 1969, marking the moment that humanity first placed a foot on a world other than its own, Apollo 11 commander Neil Armstrong began his work documenting the lunar surface before him.

The image above is the first photo taken by Armstrong after exiting Eagle, the landing module — and the first photograph ever taken by a person standing on the surface of another world.

After this image, Armstrong took several more images of the surrounding landscape before fellow astronaut Edwin “Buzz” Aldrin, Jr. exited the module as well. The third man on the mission, Michael Collins, remained in lunar orbit piloting the command module Columbia.

The rest, as they say, is history.

Armstrong, as were all the Apollo mission astronauts, was trained in the use of a modified Hasselblad 500 EL camera, which took wonderfully detailed images on large-format film. Most of the photos they brought back have been high-quality scanned by Kipp Teague and are available online at the Apollo Image Gallery.

Today is the 43rd anniversary of the first lunar landing. More than just a page in the history books, it marks a shining moment for all of humanity when the combined ingenuity and courage of many, many people succeeded in the daunting task of, in President Kennedy’s words from May 25, 1961, “landing a man on the moon and returning him safely to Earth.”

Images: NASA. Scans by Kipp Teague.