Mars through the eyes of Soujourner-Pathfinder
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SOU-SOL000-Pathfinder-LandingSite-Map.jpgChrise's Map: the Landing Site of Soujourner-Pathfinder87 visitenessun commento
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SOU-SOL001-1-Pathfinder-LandingSite-Viking1-00.jpgThe Pathfinder Landing Site, from Viking 1 (1)95 visitenessun commento
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SOU-SOL001-1-Pathfinder-LandingSite-Viking1-01.jpgThe Pathfinder Landing Site, from Viking 1 (2)113 visiteMosaic of Viking Orbiter images illustrating the location of the Pathfinder Lander (approx. 19,17° North Lat. and 33,21° West Long in the USGS ref. frame) with respect to surface features. Prominent features on the horizon include North Knob, Southeast Knob, Far Knob, Twin Peaks and Big Crater. Two small craters visible in the Orbiter and Lander views (Little Crater and Rimshot Crater) lie on the NW outer flank of the rim of Big Crater. Since the Lander is on the SE-facing flank of a low ridge, very distant features to the South and East are in view, whereas relatively nearby features to the North are partially or completely obscured. Only the tip of North Knob, which appears larger in the Viking orbiter images than the Twin Peaks, projects above the Local Horizon, and a 300-m crater, 1.2 km to the North/East, is completely obscured".
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SOU-SOL001-80808_full.jpgColor Panorama: Sol 1229 visiteUn nuovo "album" per una "vecchia" Missione: il mini-rover Soujourner, la Sonda Patrhfinder (lett.: cerca-percorso) e le loro "visioni", ora a colori (spesso brutti) ed ora in b/n (decisamente molto meglio), di Marte.
Era il 4 Luglio (ma guarda che combinazione...) 1997 quando le prime immagini del Pianeta Rosso (Ares Vallis) incominciarono ad arrivare e si trattò di frames storici poichè, come la NASA stessa ci rammenta "...these images represent Humankind's return to the Red Planet. More than 20 years after the Viking I and II Missions, Pathfinder has landed on Mars!").
Nota: le immagini da guardare e commentare coprono solo 95 Soles: 30 relativi alla "Prime Mission" - e cioè sino al 3 Agosto 1997 - ed il resto per la "Extended mission" - vale a dire sino al 9 Ottobre 1997).
Una Missione breve? Forse si e forse no.
Una Missione interessante? Giudicatelo Voi!...
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SOU-SOL001-80813_full.jpgColor Panorama: Sol 1131 visiteView of martian surface taken by the Imager for Mars Pathfinder (IMP), the camera on board the Mars Pathfinder lander. This image was taken in mid-morning on Mars (2:30 PM Pacific Daylight Time, July 4, 1997). Part of the small rover, Sojourner, is visible on the left side of the picture. The tan cylinder to the right of the rover is one of two rolled-up ramps by which the rover will descend to the ground. The white, billowy material in the center of the picture is part of the airbag system. Many rocks of different shapes and sizes are visible between the lander and the horizon. Two hills are visible on the horizon. The notch on the left side of the leftmost conical hill is an artifact of the processing of this picture.
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SOU-SOL001-80815_full.jpgColor Panorama: Sol 1123 visitePathfinder enters the upper atmosphere of Mars at 10:02 PDT and at a velocity of approx. 26.500 Km/hour and begins the sequence of events that will land the Spacecraft on the surface. From this point on, the only likely signal from the Spacecraft will be the carrier wave, a single frequency radio wave. The shifting frequency of the carrier, know as the "Doppler shift", will provide an indication of the decelerations occurring during entry and parachute deployment. The Spacecraft is also designed to send back a frequency-keyed signal following certain key events (this signal is called a "semaphore"). The semaphore is very weak and is not expected to be received in real time. However, careful analysis after-the-fact of the broad frequency spectrum recording of the radio signal will give the Operations Team considerable information on how events unfolded during the rapid descent to the surface.
Entry, descent and landing (EDL) takes approximately 4,5' and follows the sequence below:
Spacecraft rapidly decelerates in the atmosphere using the heatshield
Parachute deploys
Heat shield separates
Lander releases from backshell, descends on bridle
Radar altimeter returns information on altitude
Airbags inflate
Rocket-assisted deceleration (RAD) engines fire
Bridle cable is cut
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SOU-SOL001-80816_full.jpgColor Panorama: Sol 1160 visiteLanding on surface of Mars in Ares Vallis. Transmitter turned off shortly after landing to save power. After touchdown, the following sequence occurs: 1) Lander bounces and rolls to a stop 2) Airbags deflate and are retracted up against the petals 3) Petals open.
These events of the entry, descent and landing phase are complete between 11:32 a.m. and 12:33 p.m. PDT. A semaphore signaling the end of this phase is received via the Lander's Low-Gain Antenna.
At 2 p.m. PDT Sunrise at the Landing Site occurs. Operations begin for Sol 1 (note: Sol is a Mars day, --> such as 24 h and about 40').
The transmitter is turned on and the Spacecraft signals Earth through the Low-Gain Antenna. This communications session will contain telemetry from all engineering subsystems including the Rover and the first science data about the atmosphere taken during descent. Carrier is received at 1:55 p.m. PDT; following ground processing, actual first information are received by flight controllers at approx. 2:09 p.m. PDT.
Original caption:"In this image from the Pathfinder IMP camera, a wide diversity of rocks are strewn in the foreground. A (small) hill is visible in the distance (note: the notch within the hill is an image artifact). Airbags are seen at the lower right".
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SOU-SOL001-80817_full.jpgColor Panorama: Sol 1130 visiteOriginal caption:"This picture from Mars Pathfinder was taken at 9:30 AM in the martian morning or MLT (such as 14:30 PDT --> Pacific Daylight Time), after the Spacecraft landed on July 4, 1997. The picture shows the Sojourner Rover perched on 1 of 3 solar panels. The (mini)Rover is 65 cm (about 26") long by 18 cm (7") tall; each of its wheels is about 13 cm (5") high. The white material to the left of the front of the Rover is part of the airbag system used to cushion the landing.
Many rocks of different of different sizes can be seen in a background of reddish soil. The landing site is in the mouth of an ancient channel carved by water. The rocks may be primarily flood debris. The horizon is seen towards the top of the picture. The light brown hue of the sky results from suspended dust".
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SOU-SOL001-80839_full-2.jpgJust Landed! - Sol 1 (possible True Colors; credits: Dr G. Barca & Lunexit)57 visitenessun commentoMareKromium
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SOU-SOL001-i1246750998img0008140027.jpgRocks around the Pathfinder - Sol 1162 visiteQuesta immagine in b/n che "chiude" la Panoramica Ufficiale dei frames Pathfinder a colori ricevuti sulla Terra durante il Sol 1 (4 Luglio 1997) rappresenta un campione davvero esemplare per quella categoria di immagini che noi chiamiamo "indecifrabili".
La qualità del frame, come vedete, è pessima e, anche operando un ingrandimento davvero modesto, il risultato (l'unico) che si ottiene è quello di rendere l'immagine totalmente inguardabile. Difficile stimare, anche qualora ci volessimo accontentare di un'ampia approssimazione, la distanza e le dimensioni degli oggetti ripresi.
Un'immagine che non fornisce risposte, anzi...Stimola migliaia di domande e fa sorgere enormi dubbi (ma - non fraintendeteci - NON sulla effettività della Missione, poichè sappiamo che questo frame proviene da Marte). Dubbi che, nel tempo, da piccole crepe nelle pareti della coerenza e della fiducia nella trasparenza dei dati raccolti durante le Missioni Spaziali, diventano voragini (sovente) irreparabili.
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SOU-SOL002-80827_full.jpgBig Rock - Sol 1127 visiteOriginal caption:"This image of the Martian surface was taken by the Imager for Mars Pathfinder (IMP) before sunset on July 4 (Sol 1), the spacecraft's first day on Mars. The airbags have been partially retracted, and portions of the petal holding the undeployed rover Sojourner can be seen at lower left. The rock in the center of the image may be a future target for chemical analysis.
The soil in the foreground has been disturbed by the movement of the airbags as they retracted".
Nota: questa immagine, come le due che seguono, è relativa al Sol 1 ma è stata ricevuta sulla Terra durante il Sol 2.
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SOU-SOL002-80827_full.jpgBig Rock - Sol 1 (MULTISPECTRUM; credits: Lunexit)62 visiteUn esempio di come il "foto-mosaico" manuale realizzato dalla NASA sia uno strumento di analisi delle immagini non solo "imperfetto" (portate il frame sino al full-size e quindi guardate gli innumerevoli vizi di "cucitura" (--> "seaming") delle singole immagini -, di "luminosità" - poichè i singoli frames sono stati evidentemente ottenuti a diverse ore del giorno locale, ergo in diverse condizioni di illuminazione e, probabilmente, attraverso diversi filtri/colore - e di "messa a fuoco"), ma anche del tutto inidoneo a subire un processo di colorizzazione ex-post.
Ad ogni modo, e muovendoci al massimo delle nostre capacità di elaborazione in colori naturali ai quali viene abbinata la tecnica MULTISPECTRUM, il risultato che vedete in questo quadro lo riteniamo comunque "abbastanza buono" e "realistico" per quanto riguarda sia i colori veri e propri del Landing Site, sia per ciò che attiene la "luminosità media" del Landing Site medesimo, tenuto conto dell'ora locale (tarda, a ridosso del tramonto) della maggioranza dei frames e della stagione.MareKromium
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