Could the Re-Entry Capsule have hit Land?
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January 31, 2012
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By now, all agencies and institutions involved in the Re-entry of the Phobos-Grunt Re-Entry
have published their final reports, so it is time to have one more look at the
data that has been presented since the Spacecraft fell back to Earth on Sunday,
January 15, 2012.
The final Entry Window ranges from 17:39 to 18:08 UTC – the probe definitely fell back to Earth during this window. Russian calculations indicated Re-Entry at 17:45 UTC placing the position of orbital decay over the Pacific Ocean. Russian Officials have subsequently insisted that all of the probe fell into the pacific, some 1,150 Kilometers off the Coast of Chile. USSTRATCOM has issued an orbital decay time of 17:46 UTC +/- 1 Minute. The European Space Agency has also delivered its final report that agrees with Roscosmos’ estimations. However, it holds a surprise as well. ESA states that Phobos-Grunt crossed the 10-Kilometer Mark on its was back to Earth at 17:45 UTC +/- 7.5 Minutes. The USSTRATCOM Data set represents Orbital Decay Data corresponding to an Altitude of 80 Kilometers. From Orbital Decay to 10-Kilometers, it takes re-entering spacecraft 7 Minutes. Another 7 Minutes pass until surviving components hit the ground. Looking at the ESA estimate, orbital decay would have occurred at ~17:38 which is 7 minutes prior to the opening of the 2-minute re-entry window that USSTRATCOM has issued. |
Photo: Lavochkin Association
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Uncertainties like these are fairly common for satellite re-entries and the
margin that ESA has given is large enough for both data sets to agree with each
other.
Phobos-Grunt suffered its Orbital Decay over the Pacific Ocean, but is it valid to assume that all spacecraft components fell into the ocean?
Assuming an Orbital Decay Time of 17:46 UTC, the middle of the STRATCOM Window, Phobos-Grunt re-entered at an position of 47°S 87°W, about 1,200 Kilometers away from making Landfall over Chile. For an Orbital Decay 1 Minute later, the Spacecraft would have been 820 Kilometers away from crossing over Chile.
Dense components of satellites usually come down 800 to 1,300 Kilometers downrange from the Orbital Decay Point. Their journey back to Earth is strongly influenced by atmospherical properties like crosswinds that play a major role during atmospheric descent. This could mean that even with an ‘on-time’ orbital decay, some parts of Phobos-Grunt could have fallen over land. Should the Probe have re-entered later than 17:46 UTC, chances of debris hitting South America increase with every second that the actual orbital decay point deviated from the Window. For orbital decay at 17:47, it is probable that some objects, like small spherical tanks or dense truss segment, have impacted Chile or even Argentina which was next on Phobos-Grunt’s final Orbital Path.
Phobos-Grunt suffered its Orbital Decay over the Pacific Ocean, but is it valid to assume that all spacecraft components fell into the ocean?
Assuming an Orbital Decay Time of 17:46 UTC, the middle of the STRATCOM Window, Phobos-Grunt re-entered at an position of 47°S 87°W, about 1,200 Kilometers away from making Landfall over Chile. For an Orbital Decay 1 Minute later, the Spacecraft would have been 820 Kilometers away from crossing over Chile.
Dense components of satellites usually come down 800 to 1,300 Kilometers downrange from the Orbital Decay Point. Their journey back to Earth is strongly influenced by atmospherical properties like crosswinds that play a major role during atmospheric descent. This could mean that even with an ‘on-time’ orbital decay, some parts of Phobos-Grunt could have fallen over land. Should the Probe have re-entered later than 17:46 UTC, chances of debris hitting South America increase with every second that the actual orbital decay point deviated from the Window. For orbital decay at 17:47, it is probable that some objects, like small spherical tanks or dense truss segment, have impacted Chile or even Argentina which was next on Phobos-Grunt’s final Orbital Path.
Image: Orbitron
One major
component playing a big role in the re-entry process of Phobos-Grunt is the
Re-Entry Capsule which has been designed to withstand the destructive forces of
atmospheric entry. It can safely be assumed that the capsule made it to the
ground intact. With a mass of on 7.5 to 10 Kilograms, the capsule would not
fall into the category of objects that could reach the 1,000-Kilometer Mark
from the Spacecraft’s Decay Point, but it was specially designed to assume an
aerodynamically stable position during its descent enabling it to maintain
horizontal velocity longer than other components impacting at a significant
downrange distance. However, components of smaller size but higher density are
likely to have a longer downrange distance than the Entry Capsule. For an
orbital decay time later than 17:46, it is possible that the Entry Capsule came
down over Chile. In this matter, a 30-second deviation from final data sets
could mean substantial changes in downrange distances. In conclusion, it is
probable that components of Phobos-Grunt have impacted in South America –
assuming the Spacecraft re-entered in the 17:45 to 17:47 Window for the
80-Kilometer Pass.
Debris originating from the Phobos-Grunt Spacecraft have not been located in Chile and Argentina. Chances of finding spacecraft components are rather slim at this point as no official recovery effort will be conducted because the probe is suspected to be in the Pacific. Chance of somebody of the general public finding space debris are low as well since many components can be mistaken for ordinary debris and metal waste.
Debris originating from the Phobos-Grunt Spacecraft have not been located in Chile and Argentina. Chances of finding spacecraft components are rather slim at this point as no official recovery effort will be conducted because the probe is suspected to be in the Pacific. Chance of somebody of the general public finding space debris are low as well since many components can be mistaken for ordinary debris and metal waste.
Final Report
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Phobos-Grunt: Re-Entry Window
January 15, 2012 - 17:39 to 18:08 UTC Possible Entry Zone: Pacific Ocean; South America (Chile, Argentina, Brazil); Atlantic Ocean ***USSTRATCOM Entry Data*** Decay: January 15, 2012 - 17:46 UTC +/-1 Minute Decay Location: ~273°E 46°S (Pacific Ocean) Data Confirmed by ESA |
Entry Map
Image: Orbitron
USSTRATCOM Decay Location: Red; Earliest/Latest Decay Points: Yellow |
Phobos-Grunt's exact Entry Location remains a Mystery
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Jan 18, 2012 21:00 GMT
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No further official information has been released on the fate of the Phobos-Grunt Space that re-entered the atmosphere on Sunday.
Roscosmos is still sticking to their intial re-entry estimation of Sunday, January 15, 2012 at some point between 17:40 and 18:10 UTC with the most probable decay time of 17:45 over the Pacific Ocean, away from land masses. USSTRATCOM is also not providing any additional information as to where the spacecraft re-entered the atmosphere. The Center for Orbital and Re-Entry Debris Studies has not changed their final decay prediction of 17:52 UTC +/- 19 Minutes (see map below).
The European Space Agency that has coordinated the international committee that was in place for Phobos-Grunt Re-Entry, has also been reluctant to provide any data. Since January 16, the message ‘An update on Phobos-Grunt reentry from ESA's Space Debris Office, including an analysis on the reentry time and location, will be available shortly’ is displayed on their website. The agency is still working with Roscosmos to work out the final set of estimations - making sure the data that will be provided is valid.
More observation reports have been submitted over the past days – verifying that Phobos-Grunt was not seen in Europe at 18:18 UTC when it was supposed to have a visible pass. These reports have come from Germany and Italy. Getting multiple observation reports validates that Phobos-Grunt was indeed no longer in orbit at that time – which conflicting sources had indicated late on Sunday.
It can be assumed that the precise location of Phobos-Grunt’s orbital decay will remain a mystery and all that can be expected over the coming days are only more estimations that are based on orbital propagation.
Phobos-Grunt - Entry Ground Track
Credit: Aerospace Corporation
The Phobos-Grunt Story is not over yet
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Jan 16, 2012 - 11:00 GMT
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Update: 12:15 GMT:
Roscosmos has now issued a report indicating that Phobos-Grunt re-entered between 17:40 and 18:10 UTC on January 15 – still centering their estimation on 17:45 for an impact in the Pacific Ocean some 1,250 Kilometers offshore.
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The Story of Phobos-Grunt’s Re-Entry is far from being over as there is only one actual piece of information that was issued after re-entry as to where and when the Spacecraft plunged back to Earth.
According to Russian Media, Ballistics Experts estimated re-entry to have occurred around 17:45 UTC. It has not been confirmed that this prediction was made with live tracking data or using Orbit Propagation Tools to calculate the most probable time of Orbital Decay.
No other data has been published after re-entry. Roscosmos has issued a map just before entry that shows the groundtrack of the most likely re-entry orbit, however this was based on data acquired at 16:15 UTC. The Center of Orbital and Reentry Debris Studies issued their final pre-entry estimation at 17:30 UTC based on Data that was obtained at 16:36 UTC. This estimation predicted entry at 17:52 +/- 19 Minutes.
This final USSTRATCOM Data Point confirms that Phobos-Grunt was still in orbit at that time. At 16:36 UTC, PG was in a 125 by 112-Kilometer Orbit with a duration of 86.85 Minutes and an Inclination of 51.413 Degrees. After that, no data is available as of now. USSTRACTOM has published their final report indicating that Phobos-Grunt re-entrered between 16:59 and 17:47 UTC.
Observer reports were rare yesterday as visible passes were only occurring at remote locations. Inside the re-entry window, Phobos-Grunt was passing over South America (Chile, Argentina, Brazil), however it was passing in daylight and would have only been poorly visible when re-entering. At 18:18 UTC, reports from Germany came in that Phobos-Grunt was not seen which would indicate that it was no longer in orbit at that time. Observing a spacecraft can be quite difficult, but definitively confirming that no pass is happening needs more skills than spotting a fast-moving spacecraft in the sky, so that the credibility of the observation has to be treated carefully.
The only thing that can be assumed for certain is that Phobos-Grunt decayed some time between 17:00 UTC and 18:40 UTC – most likely on Orbit 1,096 of the mission.
Current Estimations/Predictions:
USSTRATCOM: January 15, 2012 - 16:59 to 17:47 UTC [Post Re-Entry]
Aerospace C.: January 15, 2012 - 17:52 UTC +/- 19 Minutes [Pre Re-Entry – Data: 16:36 UTC]
Roscosmos: January 15, 2012 - 17:50 to 18:34 UTC [Pre Re-Entry – 16:15 UTC]
Spaceflight101: January 15, 2012 - 17:33 UTC +/- 20 Minutes [Pre Re-Entry]
Harro Zimmer: January 15, 2012 - 18:02 UTC +/- 12 Minutes [Post Re-Entry]
Ted Molczan: January 15, 2012 - 16:37 UTC +/- 90 Minutes [Pre Re-Entry]
Roscosmos has now issued a report indicating that Phobos-Grunt re-entered between 17:40 and 18:10 UTC on January 15 – still centering their estimation on 17:45 for an impact in the Pacific Ocean some 1,250 Kilometers offshore.
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The Story of Phobos-Grunt’s Re-Entry is far from being over as there is only one actual piece of information that was issued after re-entry as to where and when the Spacecraft plunged back to Earth.
According to Russian Media, Ballistics Experts estimated re-entry to have occurred around 17:45 UTC. It has not been confirmed that this prediction was made with live tracking data or using Orbit Propagation Tools to calculate the most probable time of Orbital Decay.
No other data has been published after re-entry. Roscosmos has issued a map just before entry that shows the groundtrack of the most likely re-entry orbit, however this was based on data acquired at 16:15 UTC. The Center of Orbital and Reentry Debris Studies issued their final pre-entry estimation at 17:30 UTC based on Data that was obtained at 16:36 UTC. This estimation predicted entry at 17:52 +/- 19 Minutes.
This final USSTRATCOM Data Point confirms that Phobos-Grunt was still in orbit at that time. At 16:36 UTC, PG was in a 125 by 112-Kilometer Orbit with a duration of 86.85 Minutes and an Inclination of 51.413 Degrees. After that, no data is available as of now. USSTRACTOM has published their final report indicating that Phobos-Grunt re-entrered between 16:59 and 17:47 UTC.
Observer reports were rare yesterday as visible passes were only occurring at remote locations. Inside the re-entry window, Phobos-Grunt was passing over South America (Chile, Argentina, Brazil), however it was passing in daylight and would have only been poorly visible when re-entering. At 18:18 UTC, reports from Germany came in that Phobos-Grunt was not seen which would indicate that it was no longer in orbit at that time. Observing a spacecraft can be quite difficult, but definitively confirming that no pass is happening needs more skills than spotting a fast-moving spacecraft in the sky, so that the credibility of the observation has to be treated carefully.
The only thing that can be assumed for certain is that Phobos-Grunt decayed some time between 17:00 UTC and 18:40 UTC – most likely on Orbit 1,096 of the mission.
Current Estimations/Predictions:
USSTRATCOM: January 15, 2012 - 16:59 to 17:47 UTC [Post Re-Entry]
Aerospace C.: January 15, 2012 - 17:52 UTC +/- 19 Minutes [Pre Re-Entry – Data: 16:36 UTC]
Roscosmos: January 15, 2012 - 17:50 to 18:34 UTC [Pre Re-Entry – 16:15 UTC]
Spaceflight101: January 15, 2012 - 17:33 UTC +/- 20 Minutes [Pre Re-Entry]
Harro Zimmer: January 15, 2012 - 18:02 UTC +/- 12 Minutes [Post Re-Entry]
Ted Molczan: January 15, 2012 - 16:37 UTC +/- 90 Minutes [Pre Re-Entry]
Re-Entry Orbit of the Spacecraft
Image: Orbitron
Phobos-Grunt has re-entered
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Jan 15, 2012 - 20:00 GMT
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It has been confirmed that the Spacecraft re-entered the Atmosphere inside the USSTRATCOM Prediction Window.
More information will become available as reports come in.
More information will become available as reports come in.
Visible PG Pass
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Jan 15, 2012 - 16:30 GMT
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Heavens-Above
Re-Entry Window Open
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Jan 15, 2012 - 16:11 GMT
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The
Re-Entry window for Phobos-Grunt is now open. According to the latest
Predictions, the most probably Entry Locations are South America, the Pacific
and the Atlantic. However, PG could come down at any time from now depending on
unpredictable atmospheric variables that could cause the vehicle to dive into
the dense atmosphere earlier than expected.
All current Predictions can be found here.
The process of narrowing down the possible Entry Location will continue after Entry has been confirmed which will happen up to one hour after the event and could take as long as several hours.
All current Predictions can be found here.
The process of narrowing down the possible Entry Location will continue after Entry has been confirmed which will happen up to one hour after the event and could take as long as several hours.
Propagated Orbit
Map: Visible Pass over the Middle East
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Jan 15, 2012 - 15:00 GMT
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Heavens-Above.com
Phobos-Grunt - Data Jan. 15
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Jan 15, 2012 - 14:00 GMT
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Visible Pass over India
Heavens-Above.com
Phobos-Grunt Data - Jan 14
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Jan 14, 2012 - 23:00 GMT
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Reduced Drag could cause Re-Entry to slip
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Jan 14, 2012 - 10:20 GMT
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Phobos-Grunt
is still on its way towards the Atmosphere, however its rate of descent
decreased a little bit – presumably due to reduced drag in the uppermost parts
of the atmosphere that responds to solar activity. (Higher solar activity causes
Earth’s Atmosphere to expand and as a result, more particles are in the upper
portion of it causing more ‘air resistance’ on the satellite as it makes its
orbit.) It could also reflect a change in the spacecraft’s orientation to a
more aerodynamically efficient attitude.
These effects could appear to be minute, but they can significantly effect Phobos-Grunt's Re-Entry Time. New predictions will come in over the next couple of hours and might already show that projections have slipped to some extent – which has been the trend over the past few days as well. We’ll make a new calculation later in the day.
The Re-Entry Info site is now updated several times per day.
These effects could appear to be minute, but they can significantly effect Phobos-Grunt's Re-Entry Time. New predictions will come in over the next couple of hours and might already show that projections have slipped to some extent – which has been the trend over the past few days as well. We’ll make a new calculation later in the day.
The Re-Entry Info site is now updated several times per day.
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Satellite
Trackers and Amateur Observers might be essential in pin-pointing
Phobos-Grunt’s Re-Entry Time and Location
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Jan 12, 2012 - 21:55 GMT
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Phobos-Grunt
will re-enter the Earth’s Atmosphere in less than 3 days – that is for sure,
but the exact time and position of its fiery demise could become a secret for
all eternity. The Re-Entry will be closely monitored by Roscosmos, the Russian
Space Agency, as well as ESA that is leading the international committee in
charge of monitoring the Entry Process, and NASA along with USSTRATCOM.
One question that will be answered is how open will the Russian Space Agency be about the Re-Entry Zone of the Spacecraft. History has shown that the Soviet Union and Russia have not always been 100% honest on re-entering spacecraft that originated in the USSR or Russia. The most recent attempt to fly a Russian Spacecraft to Mars ended in disaster as well. In 1996, the Mars 96 Probe was launched aboard a Proton Rocket with a Block-D-2 Upper Stage which performed one burn to insert the Payload into orbit but failed and separated before making the second burn to inject Mars 96 into its Trajectory out of Low Earth Orbit and on to Mars. The premature separation caused the spacecraft to conduct a burn that put it into an elliptical orbit with its low point taking it into the dense atmosphere of Earth. On Orbit 3 of the doomed Mission, the Spacecraft re-entered. No pre-entry warning was issued by Russia, although they were tracking the spacecraft and were aware of its orbital parameters. |
A recent Radar Image of Phobos-Grunt acquired by the TIRA Observation Radar (Credit: Fraunhofer FHR - Link)
Photo: Fraunhofer FHR
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During a news conference - days after the event, Russian
Officials admitted that the spacecraft had re-entered and claimed that it made
an impact in the Pacific Ocean, away from any land masses. US Space
Surveillance and witnesses in South America have given strong indications that
Mars 96 came down over land. Russia did not acknowledge that and no recovery
effort was started. Where the spacecraft and the 200 grams of radioactive
Plutonium it had on-board, hit the surface remains a secret as no debris has
been found – officially.
Roscosmos has not been transparent during the initial revelations of the Mission’s Failure and time will tell how its re-entry will be handled.
USSTRATCOM is also monitoring the Probe with its Space Surveillance Network. Previous entries have shown however that Predictions of exact entry times can in some cases include large margins. For UARS in September 2011, 106 Minutes of margin were included in the final report which is only narrowing the Entry Zone down to 1.25 Orbital Paths around Earth. For the German ROSAT that re-entered in October 2011, the uncertainty was 14 Minutes which still is about 15% of the orbital period at re-entry.
That is why satellite spotters could be essential in pin-pointing the time of Phobos-Grunt's Re-Entry on Sunday by providing information on wether the spacecraft showed up on visible passes or not which would obviously mean that it is no longer up there and give some guidance for evaluations.
The final orbits of the Spaceraft will be monitored by many routine satellite trackers and observers that don’t want to miss the chance of getting a great light show, but not many locations get visible passes as the observer has to be in the dark while the spacecraft is still illuminated by the sun. Should the spacecraft enter the amtosphere over or near land, observers can expect to see it during night-time or twilight.
Help us through the usual confusion on Re-Entry Day and step outside to look for Phobos-Grunt and let us know if you saw it – Observe Phobos Grunt.
You can follow the Re-Entry via this page, our Twitter Feed and the Re-Entry Information site with latest orbit information and updated charts as events progress on Sunday.
Roscosmos has not been transparent during the initial revelations of the Mission’s Failure and time will tell how its re-entry will be handled.
USSTRATCOM is also monitoring the Probe with its Space Surveillance Network. Previous entries have shown however that Predictions of exact entry times can in some cases include large margins. For UARS in September 2011, 106 Minutes of margin were included in the final report which is only narrowing the Entry Zone down to 1.25 Orbital Paths around Earth. For the German ROSAT that re-entered in October 2011, the uncertainty was 14 Minutes which still is about 15% of the orbital period at re-entry.
That is why satellite spotters could be essential in pin-pointing the time of Phobos-Grunt's Re-Entry on Sunday by providing information on wether the spacecraft showed up on visible passes or not which would obviously mean that it is no longer up there and give some guidance for evaluations.
The final orbits of the Spaceraft will be monitored by many routine satellite trackers and observers that don’t want to miss the chance of getting a great light show, but not many locations get visible passes as the observer has to be in the dark while the spacecraft is still illuminated by the sun. Should the spacecraft enter the amtosphere over or near land, observers can expect to see it during night-time or twilight.
Help us through the usual confusion on Re-Entry Day and step outside to look for Phobos-Grunt and let us know if you saw it – Observe Phobos Grunt.
You can follow the Re-Entry via this page, our Twitter Feed and the Re-Entry Information site with latest orbit information and updated charts as events progress on Sunday.
