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Post Info TOPIC: SMART-1


L

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Impact Site
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SMART1Impact
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Credits: ESA/ US Clementine Project, BMDO, NRL, LLNL

One degree of latitude corresponds to 30 kilometres on the Moon, and one arc-second from Earth subtends 1.8 kilometres on the Moon centre.

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RE: SMART-1
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If you are a professional or amateur astronomer and want to contribute to the final phase of the SMART-1 mission, join ESA on the impact ground observation campaign.

Like most of its lunar predecessors, SMART-1 will conclude its scientific observations of the Moon through a small impact on the lunar surface. This is planned to take place in the lunar Lake of Excellence, located at mid-southern latitudes. A trim manoeuvre at the end of July has determined that the impact will most likely occur on 3 September 2006 at 07:41 CEST (05:41 UT), or at 02:36 CEST (00:36 UT) on the previous orbit due to uncertainties in the detailed knowledge of the lunar topography.

If impacting on 3 Sept at 07:41 CEST, SMART-1 will touch the Moon at the lunar coordinates 36.44º South and 46.25º West. If impacting on 3 September at 02:36 CEST the lunar coordinates will be 36.4º South and 43.5º West.

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L

Posts: 131433
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RE: SMART-1 Impact
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SMART-1, the successful first European spacecraft to the Moon, is now about to end its exploration adventure, after almost sixteen months of lunar science investigations.

SMART-1 was launched on 27 September 2003, and it reached the Moon in November 2004 after a long spiralling around Earth. In this phase, the spacecraft tested for the first time in space a series of advanced technologies.
These included the first use of an ion engine (solar electric propulsion) for interplanetary travels, in combination with gravity assist manoeuvres.
SMART-1 also tested future deep-space communication techniques for spacecraft, techniques to achieve autonomous spacecraft navigation, and miniaturised scientific instruments, used for the first time around the Moon.
Initially planned to operate six months around the Moon, SMART-1 was later given a mission extension of one further year, now about to be concluded. The spacecraft will hit the Moon surface through a small impact currently expected for 3 September 2006, at 07:41 CEST (05:41 UT) or at 02:37 CEST (00:37 UT), with an uncertainty due to the incomplete knowledge of the lunar topography. The expected coordinates for impact at 5:41 UT are about 36.44º south of latitude and 46.25º west of longitude.

If left on the course of its lunar orbit, SMART-1 would have naturally hit the Moon on 17 August 2006 on the lunar far side, not visible from Earth.
A 2-week series of manoeuvres started on 19 June and concluded on 2 July allowed SMART-1 to adjust its orbit to avoid having the spacecraft intersect with the Moon at a disadvantageous time from the scientific point of view, and to obtain a useful small mission ‘extension’.
A further series of minor manoeuvres may be performed on 27 and 28 July, 25 August and on 1 and 2 September 2006 to adjust the SMART-1 trajectory.

The choice of 3 September for lunar impact was led by the decision to obtain further high resolution lunar data from orbit and to allow ground telescopes to see the impact from Earth.
On 3 September 2006 the SMART-1 perilune, coinciding with the point of impact, will be on the lunar area called ‘Lake of Excellence’, located at mid-southern latitudes. This area is very interesting from the scientific point of view. It is a volcanic plain area surrounded by highlands, but also characterised by ground mineral heterogeneities.
At the time of impact, this area will be in the dark on the near-side of the Moon, just near the terminator – the line separating the lunar day-side from the night-side. The region will be shadowed from the Sun’s direct rays, but it will be lit faintly by the light from the Earth – by earthshine. The spacecraft’s orbit will take it over the region every five hours, getting one kilometre lower at each pass. From Earth, a Moon quarter will be visible at that time.

smartimpact
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This geometry is ideal to allow ground observations. In fact, during full Moon the luminosity would have completely obscured the impact to ground observers, and during new Moon it would have been difficult as well, because new Moon is visible only for a few seconds after sunset. Furthermore, an impact in the dark will favour the detection of the impact flash.
The ground telescopes will also try to observe the dust ejected by the impact, hoping to obtain physical and mineralogical data on the surface excavated by the spacecraft.
The expected impact time (07:41 CEST ) will be good for big telescopes in South and Northwest Americas and Hawaii and possibly Australia. But if SMART-1 hits a hill on its previous pass, around 02:37 CEST on 3 September, then it can be observed from the Canary Islands and South America. If SMART-1 hits a hill on the pass on 2 September at 21:33 CEST, then telescopes in Continental Europe and Africa will have the advantage.

When a spacecraft orbits around the Moon, as SMART-1 does, it is doomed by the law of gravity. Tugs from the Sun, the Earth, and irregularities in the Moon itself, all disturb its orbit. Sooner or later, any lunar orbiter will impact the Moon surface unless it has very big amounts of fuel left to be re-boosted and escape the lunar gravity.
To break away from the Moon’s gravity and go off into deep space would have meant cancelling the SMART-1 science programme entirely. In fact, by the time SMART-1 was in its orbit around the Moon, there was enough propellant left for an orbital boost, but not for an escape, so the spacecraft was a true ‘prisoner’ of the Moon.

SMART-1 has survived far longer than expected when the originally planned 6-month scientific mission. Its experimental ion engine, powered by the Sun, was very efficient. By the time SMART-1 had settled into its operational orbit around the Moon in March 2005 there was only 7 kilograms of propellant left (bottled xenon gas) out of the 84 kilograms available at launch.
ESA engineers used all the remaining xenon to avoid an early crash due in September 2005, after a manoeuvres to re-boost the orbit. As a result, SMART-1 gained an extra year of operational life in its lunar orbit, to the great benefit of Europe’s space scientists and engineers.
Out of xenon propellant, SMART-1 used its hydrazine thrusters to perform the last major manoeuvre at the end of June 2006 to further stretch the mission lifetime and win three more weeks of operations.

Nearly 50 years ago, in 1959, the Russian Luna-2 spacecraft was the first man-made object to hit the Moon. Since then many others have done the same, without any noticeable harm, and SMART-1’s impact will be softer than that of any man-made impactor up till now.

When it arrives at the Moon’s surface, SMART-1 will be travelling at 2 kilometres per second. That’s much slower than a natural meteoroid - for instance Leonid meteoroids arrive on the Moon at 70 kilometres per second. SMART-1 will go in at a glancing angle – like a ski jumper. SMART-1 may hit a steep hill at 7000 kilometres per hour, but what is more likely is that it will glide down over a flat part of the lunar surface, dropping 15 metres in the last kilometre of forward motion. At impact, its vertical speed will be only 70 kilometres per hour, which is less than some ski jumpers achieve.
Possibly SMART-1 will skid for a short distance after impact, throwing up dust ahead of it and spraying dust out on either side like the wings of a butterfly. The crater made by SMART-1 will be 3 to 10 metres wide and perhaps a metre deep. The Moon already has 100 000 craters that are more than four kilometres wide, and every day several small meteoroids make craters as big as SMART-1’s.
Every chemical element present on SMART-1 and in its equipment exists naturally on the Moon. For instance aluminium and iron are very common. Hydrogen, carbon and nitrogen are much scarcer on the Moon, but they arrive naturally onto the surface from the solar wind and from the impacts of icy fragments of comets, which contain many elements. From this point of view, one can think of SMART-1 as an artificial comet. Furthermore, the little hydrazine left in the SMART-1 thrusters will burn immediately at impact.

The last observations before impact will provide new impressions of the lunar landscapes.
During close lunar approaches, the AMIE camera on board SMART-1 will have oblique views of some areas that we have previously looked at only vertically, providing a sort of 3-dimensional view of the surface. However, as the impact will occur in a dark area of the Moon, it is not possible to expect to see very much by visible light during the final descent.

During the last orbits, the other instruments on-board, including the D-CIXS X-ray telescope and the SIR infrared spectrometer, will have detailed views of some lunar regions from very low altitudes.
Powerful telescopes on the Earth may see a faint flash from the impact itself, followed by a cloud of dust thrown up by the impact, perhaps 5 kilometres wide. The dust will obscure the view of part of the Moon’s surface for 5 or 10 minutes. The behaviour of the cloud will give valuable information about impact events in general, while the analysis of the light from the dust, with spectrographs in the telescopes, may detect materials dug up by the impact from just beneath the lunar surface.
The observations will rely on the faint glow of earthshine – unless some of the dust cloud is thrown more than 20 kilometres above the lunar surface. In that case, it will be lit directly by sunlight and will appear far brighter for perhaps a few minutes. Amateur astronomers may be able to spot the sunlit dust cloud with their binoculars and small telescopes.

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L

Posts: 131433
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RE: SMART-1
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In Spring this year European radio astronomers started a test observation campaign to track from Earth the trajectory of the SMART-1 spacecraft around the Moon. While other worldwide radio telescopes are now joining the campaign, the experts have started analysing the first results, precious for tracking SMART-1 up to its lunar impact and future lunar missions as well.

The campaign started on 25 May 2006, when European radio astronomers led by Dr Leonid Gurvits, from the Joint Institute for VLBI (Very Long Baseline Interferometry) in Europe (JIVE) in the Netherlands, started the spacecraft observation campaign in coordination with the ESA SMART-1 team.
The 8-hour long observing session involved three European radio telescopes - the Medicina station close to Bologna, Italy, the Metsähovi station in Kylmälä, Finland, and the Westerbork Radio Observatory at Hooghalen in The Netherlands. In particular, the Medicina station detected SMART-1 in real time, as the telescope is equipped with a real-time spectrum analyser. Further tests were also performed at Westerbork on 17 July 2006.
The test campaign proved to be very successful, and it confirmed that radio observations prior and during the SMART-1 impact are technically feasible and now fully tested with the VLBI setup.
In the meantime, a group of Chinese radio telescopes, under coordination of the Shangaii Astronomical Observatory and in collaboration with the ESA SMART-1 and the JIVE VLBI teams, have also detected and tracked the SMART-1 spacecraft. This will help the Chinese group to validate the ground stations to be used for the Chinese Chang'E1 lunar orbiter, due for launch in 2007.
Two radio telescopes in South America - TIGO station in Chile and the Fortaleza station in Brazil have also agreed to join the club of Smart-1 radio observers. Their participation is extremely valuable as they are located most favourably to conduct the observation just before and during the impact.
Under the coordination of JIVE , also the SMART-1 observing test using TIGO and Fortaleza on 15 and 16 June 2006 was successful, with the spacecraft radio signal clearly detected at both stations. The data arrived to JIVE for further analysis.

"This test proves that the setup and scheduling procedure for telescopes never before involved in this kind of observations and based on our earlier test run with the European antennas is correct" - Leonid Gurvits, leader of the JIVE team.

Indeed for both TIGO and Fortaleza this was the first experience in tracking a spacecraft. In particular, the two stations will take advantage of their favourable location to observe the SMART-1 impact, due to take place on 3 September 2006 between 02:00 and 08:00 (CEST).

"It is exciting that worldwide radio telescopes can listen to SMART-1 until impact. This also proves that SMART-1 is helping to prepare ground stations, radio telescopes and VLBI experiments for future international lunar and planetary missions" - Bernard Foing, SMART-1 Project Scientist.

The impact is due to take place on 3 September 2006 at 07:41 CEST (05:41 UT), with an uncertainty of plus or minus 7 hours.

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This image, taken by the advanced Moon Imaging Experiment (AMIE) on board ESA's SMART-1 spacecraft, shows a highly eroded highland area close to the equator on the lunar far side - the side of the Moon always facing away from Earth.

moon_L

AMIE obtained this image on 1 January 2006, from a distance of 1483 kilometres from the surface, with a ground resolution of 134 metres per pixel. The imaged area is centred at a latitude of 4.2º South and longitude 98.4º East.
The image shows some highly eroded highland areas. Many craters are almost not longer visible, as they were destroyed by subsequent impacts.

Credits: ESA

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This animation, made from images taken by the advanced Moon Imaging Experiment (AMIE) on board ESA’s SMART-1 spacecraft, shows Kepler crater on the Moon.

AMIE obtained this sequence on 13 January 2006 from a distance ranging between 1613 and 1702 kilometres from the surface, with a ground resolution between 146 and 154 metres per pixel.



The imaged area is centred at a latitude of 37.8º South and longitude 9.0º East. Kepler is a small young crater situated between Oceanus Procellarum and Mare Insularum. It has a diameter of 32 km and it is 2.6 kilometres deep.
Kepler displays a ray system that overlaps with rays from other craters and which extends over 300 kilometres. The outer wall shows a slightly polygonal shape. The interior walls of the crater are slumped and slightly terraced, and descend to an uneven floor and a minor central rise.

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After sixteen months orbiting the Moon, ESA's lunar mission is preparing for the end of its scientific exploration. On 19 June, SMART-1 mission controllers initiated a 17-day series of manoeuvres aimed at positioning the spacecraft to enhance science data return as the mission winds down.

SMART-1, Europe's successful first Moon mission, is scheduled to end on 3 September 2006, impacting on the Moon's surface in a disposal plan similar to that of many earlier lunar missions and almost three years to the day after its 2003 launch.

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L

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Crater Zucchius
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This image, taken by the advanced Moon Imaging Experiment (AMIE) on board ESA’s SMART-1 spacecraft, shows the central peaks of crater Zucchius.

AMIE obtained this image on 14 January 2006 from a distance of about 753 kilometres from the surface, with a ground resolution of 68 metres per pixel.
The imaged area is centred at a latitude of 61.3º South and longitude 50.8º West. Zucchius is a prominent lunar impact crater located near the southwest limb. It has 66 kilometres diameter, but only its inside is visible in this image, as the AMIE field of view is 35 kilometres from this close-up distance.



Because of its location, the crater appears oblong-shaped due to foreshortening. It lies just to the south-southwest of Segner crater, and northeast of the much larger Bailly walled-plain. To the southeast is the Bettinus crater, a formation only slightly larger than Zucchius.
Zucchius formed in the Copernican era, a period in the lunar planetary history that goes from 1.2 thousand million years ago to present times. Another example of craters from this period are Copernicus (about 800 milion years old) and Tycho (100 million years old). Craters from the Copernican era show characteristic ejecta ray patterns - as craters age, ejecta rays darken due to weathering by the flowing solar wind.
The hills near the centre of the image are the so-called ‘central peaks’ of the crater, features that form in large craters on the Moon. The crater is formed by the impact of a small asteroid onto the lunar surface. The surface is molten and, similarly to when a drop of water falls into a full cup of coffee, the hit surface bounces back, it solidifies and then 'freezes' into the central peak.

The name of Zucchius crater is due to the Italian Mathematician and astronomer Niccolo Zucchi (1586-1670).

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Highlands and Mare landscapes
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These two images, taken by the advanced Moon Imaging Experiment (AMIE) on board ESA’s SMART-1 spacecraft, show the difference between lunar highlands and a mare area from close by.

highlights & mares

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Credits: ESA/SMART-1/Space-X (Space Exploration Institute)

The first image, showing highlands, was obtained by AMIE on 22 January 2006, from a distance of about 1112 kilometres from the surface, with a ground resolution of 100 metres per pixel. The imaged area is centred at a latitude of 26º South and at a longitude of 157º West.

The second image, showing a mare, was taken on 10 January 2006, from a distance of about 1990 kilometres and with a ground resolution of 180 metres per pixel. The geographical coordinates of the area are 27.4º North latitude and 0.8º East.

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L

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RE: SMART-1
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Report for period 20 February to 19 March 2006

SMART-1 operations have been nominal during this period. It has been found that after an eclipse occurred on 28 October, there was a drop in the solar array +Y current of about 1.1 Amps (~52 Watts). The Swedish Space Corporation (SSC), SMART-1's industrial prime contractor, has suggested that the most probable cause is the loss of one subsection of the solar array at the +Y panel. The small reduction in power is not causing any problem for the spacecraft's day-to-day operation.

The payload operations have also run as planned and D-CIXS successfully uploaded a software patch.

SMART-1 is aiming at being the first ESA mission to command spacecraft operations automatically. The Ground Operations Automation Review (GOAR) took place on 16 March 2006. The board assigned some actions and called for a delta review to be done on 31 March.

End-of-Mission Planning

All information relevant to the impact of SMART-1 is being consolidated at the moment:

* Flight Dynamics (FD) has completed the analysis of the end-of-mission planning
* The FD analysis will be complemented with a technical note being produced by the SSC and a thermal simulation being done at ESTEC
* The SMART-1 Principal Investigator, Bernard Foing is also coordinating the Moon Smart Impact, predictions and observation campaign

Without any changes to its orbit, SMART-1 would impact the Moon around 17 August 2006. However, science requirements have asked for pushing back this date to 3 September. To achieve this extension, the perilune distance will be increased by a series of perilune raising manoeuvres from the end of June through early July. The perilune raising manoeuvre strategy details are as yet to be finalised.

The accuracies of the planned delta-V generation using RWOL doesn't allow phasing control. Consequently, the time of the selected impact perilune may shift during the perilune raising manoeuvres. If the shift exceeds a certain amount, a new perilune can be selected. To support this selection the project scientist defines a slot of 5.5 hours for the impact. This slot will always contain one and usually only one perilune.

The initial state prior to perilune raising manoeuvres, on 18 May 2006:

* Radius of perilune = 2124 km (Moon radius = 1738 km)
* Radius of apolune = 4714 km
* Coordinate system = Z-axis towards Moon north pole of date, X-axis towards descending node of Earth equator of epoch 2000 w.r.t. Moon equator of date
* Inclination = 90.6°
* Right ascension of ascending node = 239.3°
* Argument of perilune = 232.2°
* Xenon left = 0.260 kg (0.060 kg usable with special operations)
* Hydrazine left = 6.3 kg

The current plan for the perilune raising manoeuvre comprises:

* 63 revolutions with about 3 hours of intermittent thrust centred around apolune
* Thrust direction along the velocity with some in-plane tilt when away from apolune
* Total delta-V = 12.032 m s-1
* Total hydrazine usage = 2.6 kg
* Total perilune raising = 90 km
* Total duration = 14 days + 3 days (halt for orbit determination and delta-V calibration)
* Start date = 21 June 2006 (end of push broom operations)
* End date = 8 July 2006
* Slots for trim = 26-27 July 2006 and 30-31 August 2006
* Current impact time prediction = 3 September 2006, 02:00 UTC

Around impact, the perilune reduces 1.2 km per revolution. Clementine data provided by the Science and Technology Operations Centre (STOC) are used for the Moon topography. The accuracy of this model is still to be determined and should be provided by the STOC. To guarantee impact at the selected perilune, trims of the perilune altitude have to be introduced. These correct for propagation uncertainty in the perilune altitude which may be up to 1.0 km per month, caused by for example uncertainties in the Moon gravity field. Without these trims, impact may occur 1 revolution earlier or later.

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