EDL songs...hmm...Rock Lobster? (down, down, down!)
Full Version: InSight Cruise Phase
Thanks for the insight (rimshot!) as always, Propguy.
EDL songs...hmm...Rock Lobster? (down, down, down!)
EDL songs...hmm...Rock Lobster? (down, down, down!)
QUOTE (propguy @ Nov 19 2018, 04:38 PM) 
Any good ideas?
"Eight Miles High" by the Byrds?
Going Down, Jeff Beck
"Well I'm going down
Down, down, down, down, down
I'm going down
Down, down, down, down, down
I've got my head out the window
And my big feet on the ground"
It's even 7 minutes long. And play it LOUD!!!
Paolo
"Well I'm going down
Down, down, down, down, down
I'm going down
Down, down, down, down, down
I've got my head out the window
And my big feet on the ground"
It's even 7 minutes long. And play it LOUD!!!
Paolo
The Rasmus - F-F-F-Falling
"I need a flame, I need a spark
Don't be afraid to open my heart
I need a game, I need a shock
Don't be afraid my heart is unlocked
Made up my mind 'bout the music
Made up my mind 'bout the style
I know that I'm stable and able
To settle down
F-f-falling"
"I need a flame, I need a spark
Don't be afraid to open my heart
I need a game, I need a shock
Don't be afraid my heart is unlocked
Made up my mind 'bout the music
Made up my mind 'bout the style
I know that I'm stable and able
To settle down
F-f-falling"
QUOTE (propguy @ Nov 20 2018, 01:38 AM)
Latest status. We did TCM5 yesterday
Good to hear that.
I just found out a weird thing I did not know: during travel toward Mars, probes are not oriented as we see in all videos, but in such a way that solar panels are correctly oriented toward sun, then the "tip turn" (which I would call "Entry Attitude Setup Maneuver") is performed.
I also read that only a short time before Phoenix arrival at atmosphere interface somebody thought that there was a possibility of recontact between cruise stage (or parts of it) and lander after lander deployment, as they're both on same ballistic trajectory, and cruise module is only slightly slowed down by the pyro devices during lander deployment: it was calculated a minimum distance of 6 meters between lander and cruise module during EDL!
So, if I understand correctly, now the lander deployment is performed before EASM, so cruise module is not just slowed down by lander deployment, but it is also put on a different trajectory due to the transverse force impressed by pyro devices; is this interpretation correct?
But if this "Cruise Module Avoidance Maneuver" was introduced only with Phoenix... how did it go for Pathfinder and MERs?
And I wonder if cruise stage falling parts could have messed up Schiaparelli descent.
During Phoenix EDL they also figured out through simulation that thrusters in the backshell can't be used as designed (i.e. during hypersonic phase), because simulations showed that due to "werid" aerodynamic effects and interactions at high speed they could result in a force being applied to the lander in the OPPOSITE direction w.r.t. what the thrusters were supposed to do! So they were not used at all during descent, unless an "emergency situation" was encountered.
These are all interesting manuevers and "rocket science things" which I've never seen in any video, but they would look much more interesting in a video than in a PDF!
Found another interesting page, which makes more simple to use SPICE (I don't know anything about SPICE but I was able to gather some data):
https://wgc.jpl.nasa.gov:8443/webgeocalc/#StateVector
Unfortunately I can't find data for Insight and Phoenix.
Phoenix is "-84" and Insight is "-189".
https://wgc.jpl.nasa.gov:8443/webgeocalc/#StateVector
Unfortunately I can't find data for Insight and Phoenix.
Phoenix is "-84" and Insight is "-189".
QUOTE (mcmcmc @ Nov 20 2018, 03:02 AM)
Good to hear that.
I just found out a weird thing I did not know: during travel toward Mars, probes are not oriented as we see in all videos, but in such a way that solar panels are correctly oriented toward sun, then the "tip turn" (which I would call "Entry Attitude Setup Maneuver") is performed.
I also read that only a short time before Phoenix arrival at atmosphere interface somebody thought that there was a possibility of recontact between cruise stage (or parts of it) and lander after lander deployment, as they're both on same ballistic trajectory, and cruise module is only slightly slowed down by the pyro devices during lander deployment: it was calculated a minimum distance of 6 meters between lander and cruise module during EDL!
So, if I understand correctly, now the lander deployment is performed before EASM, so cruise module is not just slowed down by lander deployment, but it is also put on a different trajectory due to the transverse force impressed by pyro devices; is this interpretation correct?
But if this "Cruise Module Avoidance Maneuver" was introduced only with Phoenix... how did it go for Pathfinder and MERs?
And I wonder if cruise stage falling parts could have messed up Schiaparelli descent.
During Phoenix EDL they also figured out through simulation that thrusters in the backshell can't be used as designed (i.e. during hypersonic phase), because simulations showed that due to "werid" aerodynamic effects and interactions at high speed they could result in a force being applied to the lander in the OPPOSITE direction w.r.t. what the thrusters were supposed to do! So they were not used at all during descent, unless an "emergency situation" was encountered.
These are all interesting maneuvers and "rocket science things" which I've never seen in any video, but they would look much more interesting in a video than in a PDF!
I just found out a weird thing I did not know: during travel toward Mars, probes are not oriented as we see in all videos, but in such a way that solar panels are correctly oriented toward sun, then the "tip turn" (which I would call "Entry Attitude Setup Maneuver") is performed.
I also read that only a short time before Phoenix arrival at atmosphere interface somebody thought that there was a possibility of recontact between cruise stage (or parts of it) and lander after lander deployment, as they're both on same ballistic trajectory, and cruise module is only slightly slowed down by the pyro devices during lander deployment: it was calculated a minimum distance of 6 meters between lander and cruise module during EDL!
So, if I understand correctly, now the lander deployment is performed before EASM, so cruise module is not just slowed down by lander deployment, but it is also put on a different trajectory due to the transverse force impressed by pyro devices; is this interpretation correct?
But if this "Cruise Module Avoidance Maneuver" was introduced only with Phoenix... how did it go for Pathfinder and MERs?
And I wonder if cruise stage falling parts could have messed up Schiaparelli descent.
During Phoenix EDL they also figured out through simulation that thrusters in the backshell can't be used as designed (i.e. during hypersonic phase), because simulations showed that due to "werid" aerodynamic effects and interactions at high speed they could result in a force being applied to the lander in the OPPOSITE direction w.r.t. what the thrusters were supposed to do! So they were not used at all during descent, unless an "emergency situation" was encountered.
These are all interesting maneuvers and "rocket science things" which I've never seen in any video, but they would look much more interesting in a video than in a PDF!
We do jettison the cruise stage prior to the slew to entry attitude (what you call EASM). That event occurs roughly 30 seconds before the slew begins, which is about 6-7 minutes prior to the start of entry. I am not allowed by ITAR to discuss the why or how come we decided to do that (sorry). I can say that all the EDL monte carlo sims also look for cruise stage contract and flag those runs, so it is not something we have missed or have forgotten. From the limited info I know about the Schiaparelli failure this is an unrelated topic (the publicly available report EXOMARS 2016 - Schiaparelli Anomaly Inquiry shows their failure was due to high rates on the parachute swamping some fault protection values for rates and thus the IMU data was ignored and they miss estimated altitude and shut off the descent engines too early). I doubt any rate that could come from contact with the cruise stage prior to entry could result in rates that created an issue at parachute deployment while still allowing for a successful entry portion (where angles of attack are very narrow for survival).
Regarding the roll reversal issue on the RCS thruster in hypersonic. That was a predict on Phoenix that came out of some a CFD analysis (see page 12 of this paper Analysis of effectiveness of phoenix entry reaction ... - NTRS - NASA). No one is sure if that is accurate or not, but to be safe Phoenix (and InSight) inhibit thruster usage after a certain time in the entry portion to avoid any potential issue. The only thing the RCS would be doing a that time anyway is roll control and as opposed to MSL we do not have a tight roll control requirement on entry (just don't spin up like a top).
QUOTE (propguy @ Nov 20 2018, 08:53 PM)
From the limited info I know about the Schiaparelli failure this is an unrelated topic (the publicly available report EXOMARS 2016 - Schiaparelli Anomaly Inquiry shows their failure was due to high rates on the parachute swamping some fault protection values[...]
I imagine debris from cruise stage falling over the open parachute amd causing a mess.
Anyway, in the meantime I slightly updated my simulator, now you can see something moving eventually! :-)
http://win98.altervista.org/space/explorat...-simulator.html
Unfortunately data at low altitude are quite low in precision.
It's a pity I have no time to further study and process telemetry data to get a yaw/pitch/roll graphical representation, maybe I'll do on real Insight data once available; for now I can try adding acceleration, and possibly atmosphere data (temp, pressure and density), all contained in same PHXPROFILES.TAB file.
I also see "attack angle" in PHXPROFILES.TAB, I wonder if I can turn it into an image of Phoenix/Insight rotating while going down in these remaining 4 days.
QUOTE (mcmcmc @ Nov 20 2018, 02:07 PM)
I imagine debris from cruise stage falling over the open parachute amd causing a mess.
Not a statistically likely event. For InSight, the cruise stage separates before the turn to entry - it's not directly following InSight into the atmosphere.
QUOTE
Anyway, in the meantime I slightly updated my simulator, now you can see something moving eventually! :-)
http://win98.altervista.org/space/explorat...-simulator.html
http://win98.altervista.org/space/explorat...-simulator.html
Both the image and the URL are missing...
The requested URL /space/exploration/insight/screenshot1.png was not found on this server.
The requested URL /space/exploration/insight/insight-edl-simulator.html was not found on this server.
Does anyone know what happens to MarCO-A & MarCO-B after they complete the communications relay of the InSight EDL data?
Is there any more science planned? Or do they simply head away from Mars basically following the cruise stage?
Is there any more science planned? Or do they simply head away from Mars basically following the cruise stage?
QUOTE (propguy @ Nov 19 2018, 04:38 PM)
On a side note, I have been trying to come up with a good EDL song to play that day on the way into work.
Bruce Springsteen
I'M GOIN' DOWN
We sit in the car outside your house, I can feel the heat coming 'round
I go to put my arm around you and you give me a look like I'm way out of bounds
Well, you let out one of your bored sighs, well lately when I look into your eyes
I'm going down, down, down, down
I'm going down, down, down, down
I'm going down, down, down, down
I'm going down, down, down, down
https://www.youtube.com/watch?v=3fdZWbIsrFk
QUOTE (PaulH51 @ Nov 21 2018, 04:32 AM)
Or do they simply head away from Mars basically following the cruise stage?
I think the cruise stage re-enters with the lander
QUOTE (PaulH51 @ Nov 21 2018, 03:32 AM)
Does anyone know what happens to MarCO-A & MarCO-B after they complete the communications relay of the InSight EDL data?
Is there any more science planned? Or do they simply head away from Mars basically following the cruise stage?
Is there any more science planned? Or do they simply head away from Mars basically following the cruise stage?
They are in the orbit of the upper stage, not the cruise stage.
Hello again ... those who have been here a decade ago(!) for Phoenix may remember my realtime simulations. They've been running since, however I was too busy at work to further develop them, but I am once again sacrificing sleep trying for a new home for them and managed to get one up for InSight (fingers crossed bug-free):
https://spaceoutreach.com/spaceflight/insight/
Note times are SCET (I dont have time to do ERT) and Entry Interface is inferred from the published trajectory data. Also, my main interest is in the astrodynamics of it all, i.e. until we hit entry interface, so EDL data may not make it into the sim in time for landing.
Re cruise stage, it separates too close to Mars to deflect it, so it will trail (I presume) InSight and burn up in the atmosphere. If the separation speed is 1m/s (I think it's more in reality), it will be almost 500 meters behind InSight, and has lots more drag so even if something isnt burning up it will not match the downrange of Insight itself.
Dont forget to buy peanuts.
https://spaceoutreach.com/spaceflight/insight/
Note times are SCET (I dont have time to do ERT) and Entry Interface is inferred from the published trajectory data. Also, my main interest is in the astrodynamics of it all, i.e. until we hit entry interface, so EDL data may not make it into the sim in time for landing.
Re cruise stage, it separates too close to Mars to deflect it, so it will trail (I presume) InSight and burn up in the atmosphere. If the separation speed is 1m/s (I think it's more in reality), it will be almost 500 meters behind InSight, and has lots more drag so even if something isnt burning up it will not match the downrange of Insight itself.
Dont forget to buy peanuts.
QUOTE (MahFL @ Nov 21 2018, 06:48 PM)
They are in the orbit of the upper stage, not the cruise stage.
I'm not sure how much they adjusted that trajectory, but they both completed at least one trajectory-correction maneuver after they separated from the upper stage, see this (Link)
The reports I have read, state that their mission will end shortly after the Insight EDL communication link is completed, I was just curious if there were any other science activities planned before their mission ends. For example, could they use any of the remaining thruster propellants to point their camera at Mars as they pass by? Be great outreach if they could do that
QUOTE (djellison @ Nov 20 2018, 11:41 PM)
Not a statistically likely event. For InSight, the cruise stage separates before the turn to entry - it's not directly following InSight into the atmosphere.
For Phoenix it was calculated a minimum distance of 6 meters between cruise stage (or its debris) and the lander during EDL, before they uploaded the corrective maneuver.
QUOTE (djellison @ Nov 20 2018, 11:41 PM)
Both the image and the URL are missing...
The requested URL /space/exploration/insight/screenshot1.png was not found on this server.
The requested URL /space/exploration/insight/insight-edl-simulator.html was not found on this server.
The requested URL /space/exploration/insight/screenshot1.png was not found on this server.
The requested URL /space/exploration/insight/insight-edl-simulator.html was not found on this server.
of course! I forgot the server name...
http://win98.altervista.org/space/explorat...-simulator.html
QUOTE (dmuller @ Nov 21 2018, 12:05 PM)
my main interest is in the astrodynamics of it all, i.e. until we hit entry interface, so EDL data may not make it into the sim in time for landing.
Good because I wasn't able to find any data for pre-entry phase!
QUOTE (PaulH51 @ Nov 21 2018, 06:11 AM)
For example, could they use any of the remaining thruster propellants to point their camera at Mars as they pass by? Be great outreach if they could do that
They already took images of Earth after departure, and there was one of Mars approach as well back at the start of October ( https://www.jpl.nasa.gov/news/news.php?feature=7263 ). It would be nice to see just one more, though since their main mission is data relay, it's hard to say if we can get an 'approach movie' that doesn't interrupt that.
Can anybody help? I found this description:
But I can't find this RDR_DATA folder it refers to.
Apart from the wrong unit of measure, the highlighted data could be possibly more precise than radial distance from Mars center I'm currently using for the simulator.
QUOTE
The Level 2 data files in the RDR_DATA subdirectory contain the following data:
Spacecraft Clock count: Units = seconds
Relative time from a defined entry state: Units = seconds
The altitude of the spacecraft above the landing site: Units = seconds
Planetocentric latitude of the spacecraft at the time of sample acquisition: Units = degrees
Planetocentric east longitude of the spacecraft at the time of sample acquisition: Units = degrees
Speed of the Phoenix entry probe at the given location: Units = m/s
Spacecraft Clock count: Units = seconds
Relative time from a defined entry state: Units = seconds
The altitude of the spacecraft above the landing site: Units = seconds
Planetocentric latitude of the spacecraft at the time of sample acquisition: Units = degrees
Planetocentric east longitude of the spacecraft at the time of sample acquisition: Units = degrees
Speed of the Phoenix entry probe at the given location: Units = m/s
But I can't find this RDR_DATA folder it refers to.
Apart from the wrong unit of measure, the highlighted data could be possibly more precise than radial distance from Mars center I'm currently using for the simulator.
QUOTE (PaulH51 @ Nov 21 2018, 12:11 PM)
For example, could they use any of the remaining thruster propellants to point their camera at Mars as they pass by? Be great outreach if they could do that
BTW, will MRO be in good position for this EDL?
Yes, 3 minutes before touchdown an image will be attempted (see Emily's excellent write-up): http://www.planetary.org/blogs/emily-lakda...ng-preview.html
QUOTE (PaulH51 @ Nov 20 2018, 07:32 PM)
Does anyone know what happens to MarCO-A & MarCO-B after they complete the communications relay of the InSight EDL data?
Is there any more science planned? Or do they simply head away from Mars basically following the cruise stage?
Is there any more science planned? Or do they simply head away from Mars basically following the cruise stage?
The cruise stage enters Mars and burns up (maybe a few pieces will survive to impact)
MarCO A and B each get a little gravity assist that changes their trajectory - so they start getting further and further apart from one another.
From an engineering perspective, I believe the intent is to keep in contact with them for as long as they hold up. At some point their prop systems will be exhausted and they'll no longer be able to maintain pointing for solar power and comms - and they'll go silent.
(InSight, MarCO A and B are all in Eyes on the Solar System......there just isn't a landing module for InSight like there was for Curiosity)
They have cameras. They'll be flying by Mars. Fingers crossed...there will be pics.
QUOTE (Explorer1 @ Nov 21 2018, 04:50 PM)
Yes, 3 minutes before touchdown an image will be attempted (see Emily's excellent write-up): http://www.planetary.org/blogs/emily-lakda...ng-preview.html
Who better than you can know?
(nice avatar)QUOTE (mcmcmc @ Nov 21 2018, 03:46 PM)
...But I can't find this RDR_DATA folder it refers to...
Maybe this document, and the according server and directories could be a better point to start from.
See also this LBL file together with this table.
QUOTE (djellison @ Nov 22 2018, 12:27 AM)
They have cameras. They'll be flying by Mars. Fingers crossed...there will be pics.
Fingers and Toes crossed
Thanks for the info Doug
QUOTE (PaulH51 @ Nov 21 2018, 03:47 PM)
Fingers and Toes crossed
And then some......
Spoiler alert - I'm helping with planning and processing of pics from their tiny camera. Trying our best to estimate reasonable exposure times in the next 48hrs before committing on Sat AM.
QUOTE (djellison @ Nov 22 2018, 09:49 AM)
...before committing on Sat AM.
Excellent news indeed
QUOTE (Gerald @ Nov 21 2018, 06:18 PM)
Maybe this document, and the according server and directories could be a better point to start from.
See also this LBL file together with this table.
See also this LBL file together with this table.
Yes, that table (and PHXPROFILES) is all I was able to find, but I think they do not match with that description.
In this file you find the list of all fields:
QUOTE
PHXPROFILE.TAB contains the following items.
Time (relative to reference time, seconds) UTC_TIME
Radial distance (m) RADIAL_DISTANCE
Areocentric latitude (degrees north) LATITUDE
Areocentric longitude (degrees east) LONGITUDE
X-component of position (m) X_POSITION
Y-component of position (m) Y_POSITION
Z-component of position (m) Z_POSITION
Element 0 of quaternion (dimensionless) Q0
Element 1 of quaternion (dimensionless) Q1
Element 2 of quaternion (dimensionless) Q2
Element 3 of quaternion (dimensionless) Q3
X-component of velocity (m/s) X_VELOCITY
Y-component of velocity (m/s) Y_VELOCITY
Z-component of velocity (m/s) Z_VELOCITY
Speed of spacecraft relative to atmosphere (m/s) VREL
X-component of acceleration (m s^(-2)) X_ACCELERATION
Y-component of acceleration (m s^(-2)) Y_ACCELERATION
Z-component of acceleration (m s^(-2)) Z_ACCELERATION
Angle of attack (degrees) ALPHA
Axial force coefficient, CA (dimensionless) CA
Normal force coefficient, CN (dimensionless) CN
Mach number (dimensionless) MA
Knudsen number (dimensionless) KN
Density (kg m^(-3)) RHO
Pressure (Pa) PRESS
Temperature (K) TEMP
Time (relative to reference time, seconds) UTC_TIME
Radial distance (m) RADIAL_DISTANCE
Areocentric latitude (degrees north) LATITUDE
Areocentric longitude (degrees east) LONGITUDE
X-component of position (m) X_POSITION
Y-component of position (m) Y_POSITION
Z-component of position (m) Z_POSITION
Element 0 of quaternion (dimensionless) Q0
Element 1 of quaternion (dimensionless) Q1
Element 2 of quaternion (dimensionless) Q2
Element 3 of quaternion (dimensionless) Q3
X-component of velocity (m/s) X_VELOCITY
Y-component of velocity (m/s) Y_VELOCITY
Z-component of velocity (m/s) Z_VELOCITY
Speed of spacecraft relative to atmosphere (m/s) VREL
X-component of acceleration (m s^(-2)) X_ACCELERATION
Y-component of acceleration (m s^(-2)) Y_ACCELERATION
Z-component of acceleration (m s^(-2)) Z_ACCELERATION
Angle of attack (degrees) ALPHA
Axial force coefficient, CA (dimensionless) CA
Normal force coefficient, CN (dimensionless) CN
Mach number (dimensionless) MA
Knudsen number (dimensionless) KN
Density (kg m^(-3)) RHO
Pressure (Pa) PRESS
Temperature (K) TEMP
QUOTE
PHXCOMPACT.TAB contains the following items.
Radial distance (m) MRADIAL_DISTANCE
Altitude (km) MALTITUDE
Density (kg m^(-3)) MRHO
Pressure (Pa) MPRESS
Temperature (K) MTEMP
Radial distance (m) MRADIAL_DISTANCE
Altitude (km) MALTITUDE
Density (kg m^(-3)) MRHO
Pressure (Pa) MPRESS
Temperature (K) MTEMP
The description in my previous post says:
QUOTE
Spacecraft Clock count: Units = seconds
Relative time from a defined entry state: Units = seconds
The altitude of the spacecraft above the landing site: Units = seconds
Planetocentric latitude of the spacecraft at the time of sample acquisition: Units = degrees
Planetocentric east longitude of the spacecraft at the time of sample acquisition: Units = degrees
Speed of the Phoenix entry probe at the given location: Units = m/s
Relative time from a defined entry state: Units = seconds
The altitude of the spacecraft above the landing site: Units = seconds
Planetocentric latitude of the spacecraft at the time of sample acquisition: Units = degrees
Planetocentric east longitude of the spacecraft at the time of sample acquisition: Units = degrees
Speed of the Phoenix entry probe at the given location: Units = m/s
So I think they are different datasets.
-------------------------
I got weird results while turning "angle of attack" data into something graphical, i.e. an image of the lander rotating as per AoA data, so then I analysed visually last seconds of the data and also plotted them, and they're weird: how can AoA become greater than 90°? (AoA is column 2x19=38 in PHXPROFILES.TAB). It also remaines greater than 90° after landing.
Definition:
QUOTE
The angle of attack, namely the angle between the spacecraft symmetry axis and the
vector velocity of the atmosphere relative to the spacecraft, was also determined using the
assumption that the atmosphere rotates with the solid body of the planet.
vector velocity of the atmosphere relative to the spacecraft, was also determined using the
assumption that the atmosphere rotates with the solid body of the planet.
Translation: angle w.r.t ground.
In the animation I obtained by rotating the image of spacecraft in realtime according to AoA (animation not yet online) it's clearly visible the effect of the engines being turned on (vibration of the lander), so one can assume that AoA>90° is due to backshell avoidance maneuver, but I expected AoA to become again 90° at landing, but it last value is 132°.
These links provide raw numerical data for MARCO-A (code "-65") and MARCO-B (code "-66") as per NASA Horizons site.
Position & speed are expressed w.r.t. Mars center.
Position & speed are expressed w.r.t. Mars center.
QUOTE (djellison @ Nov 21 2018, 05:49 PM)
And then some...... Spoiler alert - I'm helping with planning and processing of pics from their tiny camera.
Spoiler alert - I'm helping with planning and processing of pics from their tiny camera.Just make sure you don't get your thumb or the camera strap in the images and you should be OK.
QUOTE (djellison @ Nov 22 2018, 02:49 AM)
And then some...... Spoiler alert - I'm helping with planning and processing of pics from their tiny camera. Trying our best to estimate reasonable exposure times in the next 48hrs before committing on Sat AM.
Spoiler alert - I'm helping with planning and processing of pics from their tiny camera. Trying our best to estimate reasonable exposure times in the next 48hrs before committing on Sat AM.Don't forget the switch to turn the images upside-down (somebody said on july 20th, 1969...) ;-)
Forum note: The EDL thread will go live at 0800 PST (1600 GMT) this Monday, 26 Nov, and discussion concerning that will happen there. Will post a link to it then.
Added manometers for deceleration and attack angle.
http://win98.altervista.org/space/explorat...-simulator.html
It's cool to see even parachute oscillations and legs deployment in the "amplified" accelerometer! (first gauge)
Paper says attack angle is unreliable after chute deployment, I don't know why.
http://win98.altervista.org/space/explorat...-simulator.html
It's cool to see even parachute oscillations and legs deployment in the "amplified" accelerometer! (first gauge)
Paper says attack angle is unreliable after chute deployment, I don't know why.
QUOTE (mcmcmc @ Nov 22 2018, 10:15 PM)
Paper says attack angle is unreliable after chute deployment, I don't know why.
from official papers it results that even NASA does not why attack angle data are totally unreliable after parachute deployment, but i can't find any further update after 2010.
There are 3 different issues on attack angle reconstruction:
1) discrepancies between predicted and re-constructed angles of attack addressed by Desai et al.(2008).
2) discrepancies (+/- 2° , which could be "explained" by a 300 m/s wind) between results from direct reconstruction from gyros and indirect reconstruction from accelerometers - "Results from the Phoenix Atmospheric Structure Experiment" Paul Withers and David Catling - 2010
3) nonsense values of angle attack at parachute deployment (46°) and after (up to 132°) - "Production of Reduced Data Records for the Phoenix Atmospheric Structure Experiment" - Paul Withers, D. C. Catlingb -
From data it also appears that Phoenix touched ground... 1.2 km above ground ("Results from the Phoenix Atmospheric Structure Experiment" Paul Withers and David Catling - 2010). I'm not sure if they are talking about "above MOLA level" or "above ground level".
MSL EDL data just stop at 12 km above surface.
I've yet to examine EDL data for MPF, MER, and Schiaparelli, anyway last part of EDLs looks quite "mysterious" yet. Still a lot of work to do till safe manned capsule landing on Mars!
Now I am very curious about what Insight EDL data will show.
----------------
I also found another interesting paper about an unexpected issue on Phoenix mission: descent radar locking on jettisoned heatshield and thus providing false values for altitude!
"Phoenix Landing Radar Heatshield Anomaly" - J. Eric Belz, Curtis Chen, and Ben Cichy
Together with high possibility of Phoenix cruise stage recontact with Phoenix lander during EDL, it's an issue I was totally unaware of till a week ago.
Just to better know what Insight is about to face:
Overview of the Phoenix Entry, Descent, and Landing System Architecture - Myron R. Grover III, Benjamin D. Cichy
Overview of the Phoenix Entry, Descent, and Landing System Architecture - Myron R. Grover III, Benjamin D. Cichy
For the Google Mars community, here is a KMZ file with InSight's landing ellipse.
Unfortunately, Google Mars does not have any CTX registered for this area, so I suggest going to GE's left panel and in the Layers section, select under Global Maps the Daytime Infrared. This is the base map appearing, for instance, in landing ellipse image contained in the press kit.
To install the file, download it to your favorite location and double click it. This should startup Google Earth, if not already opened, and initiate a switch to Google Mars (a pop-up will display). The globe should automatically rotate and position itself over the ellipse area. Acknowledgements, credits, and a short explanation are available on the file's help panel. To get to the panel select the file's name on GE's Places panel.
The ellipse is approximated by a 180-sided polygon. I'd welcome information on any errors that may exist.
Fernando
Click to view attachment
Unfortunately, Google Mars does not have any CTX registered for this area, so I suggest going to GE's left panel and in the Layers section, select under Global Maps the Daytime Infrared. This is the base map appearing, for instance, in landing ellipse image contained in the press kit.
To install the file, download it to your favorite location and double click it. This should startup Google Earth, if not already opened, and initiate a switch to Google Mars (a pop-up will display). The globe should automatically rotate and position itself over the ellipse area. Acknowledgements, credits, and a short explanation are available on the file's help panel. To get to the panel select the file's name on GE's Places panel.
The ellipse is approximated by a 180-sided polygon. I'd welcome information on any errors that may exist.
Fernando
Click to view attachment
QUOTE (nogal @ Nov 23 2018, 05:09 PM)
For the Google Mars community
Damn!
If just you'd remebered me before about existence of Google Earth, I could have set up something better than this....
I totally forgot that I can create animations in google earth!
This is the Phoenix EDL:
http://win98.altervista.org/space/explorat...Phoenix-EDL.kmz
It's even possibile to make the marker shape change depending on altitude, and shift whole trajectory to Insight site (just for fun, it's a simulator)... but I think it would require more time than remaining time to the event. :-(
In case anybody has time/wish to help, this is the source code which converts EDL data into KML format:
http://win98.altervista.org/space/explorat...t/crea-EDL.html
Data are here:
http://win98.altervista.org/space/explorat...ht/js/coords.js
Taken as usual from PHXPROFILES.TAB .
This line gets one sample every 200 to make things faster; change "200" to "1" for a realtime animation:
CODE
for (index = 0; index <= latLonAlt.length-1; index += 200) {
I believe that angle of attack information after chute deployment is irrelevant. The aeroshell is no longer providing any significant lift; it's all about the inflated chute at that point, which had better be normal to the flight path.
QUOTE (nprev @ Nov 23 2018, 09:20 PM)
I believe that angle of attack information after chute deployment is irrelevant.
Irrelevant for what?
It doesn't actually matter. The s/c will be swinging backwards and forwards under the parachute. It's 'angle of attack' isn't really a thing any more. The s/c uses the IMU at this point to interpret RADAR data, but the actual angle really doesn't matter.
Another way to put it: The angle of attack of the parachute with respect to prevailing airflow should be 90 deg.
QUOTE (mcmcmc @ Nov 23 2018, 06:58 PM)
Damn!
If just you'd remebered me before about existence of Google Earth, I could have set up something better than this....
I totally forgot that I can create animations in google earth!
If just you'd remebered me before about existence of Google Earth, I could have set up something better than this....
I totally forgot that I can create animations in google earth!
Here it is, quick and dirty, using Phoenix's EDL data (rotated and re-centered). You have to play with the slider controls to see the full path. Maybe I'll polish it latter but right now it is way past my shuteye time. Cheers
Fernando
Click to view attachment
QUOTE (nogal @ Nov 24 2018, 03:23 AM)
Here it is, quick and dirty, using Phoenix's EDL data (rotated and re-centered). You have to play with the slider controls to see the full path. Maybe I'll polish it latter but right now it is way past my shuteye time. Cheers
Fernando
Click to view attachment
Fernando
Click to view attachment
Cool.
We should also find a method to:
- make a real time video (Google Earth settings do not allow a speed lower than "10 seconds per second")
- make markers representing different phases of the landing (I have the images, I have tocleanup them and see if I can make their background transparent)
- add camera orientation to each point to create kind of a movie centered on lander
In the meantime, I have to finish the other simulator.
All in around 55h.
QUOTE
It doesn't actually matter. The s/c will be swinging backwards and forwards under the parachute. It's 'angle of attack' isn't really a thing any more. The s/c uses the IMU at this point to interpret RADAR data, but the actual angle really doesn't matter.
The point is: if you are going to land on Mars (not "generic you", but you nprev or djellison), wouldn't you like to know in advance how your spaceship/spacecraft/aircraft/whatelse will be oriented during final descent? I would. All this EDLs have to be (also) interpreted as test for future manned landings, but we currently don't know anything about lander attitude between parachute deployment and landing.
Additionally, an error in merging and crossprocessing radar data and IMU data by GNC caused fatal failure of Exomars 2016, so design needs a little improvement for this phase, IMHO.
NASA horizons data about Insight usually stopped after 2018-11-26 20:40, and they did not implement at all the landing.
Now they say that landing will happen on november 25th?!?
2458448.318055556, A.D. 2018-Nov-25 19:38:00.0000, 9.125119431869558E-01, 2.735641984023738E+05, -3.024901901551133E+00,
2458448.318750000, A.D. 2018-Nov-25 19:39:00.0000, 9.119065406414170E-01, 2.733827032851672E+05, -3.024935345862831E+00,
2458448.319444444, A.D. 2018-Nov-25 19:40:00.0000, 1.131818709765760E-02, 3.393107130110657E+03, 4.196530165013691E-14,
2458448.320138889, A.D. 2018-Nov-25 19:41:00.0000, 1.131818656712531E-02, 3.393106971061080E+03, -5.212723928404643E-06,
4th datum is distance in km from Mars center; Phoenix landing site in Phoenix EDL data is stated as to be 3376.3 km distant from Mars center, so 3rd line here above appears to describe a landing happening at right time but in wrong date.
Now they say that landing will happen on november 25th?!?
2458448.318055556, A.D. 2018-Nov-25 19:38:00.0000, 9.125119431869558E-01, 2.735641984023738E+05, -3.024901901551133E+00,
2458448.318750000, A.D. 2018-Nov-25 19:39:00.0000, 9.119065406414170E-01, 2.733827032851672E+05, -3.024935345862831E+00,
2458448.319444444, A.D. 2018-Nov-25 19:40:00.0000, 1.131818709765760E-02, 3.393107130110657E+03, 4.196530165013691E-14,
2458448.320138889, A.D. 2018-Nov-25 19:41:00.0000, 1.131818656712531E-02, 3.393106971061080E+03, -5.212723928404643E-06,
4th datum is distance in km from Mars center; Phoenix landing site in Phoenix EDL data is stated as to be 3376.3 km distant from Mars center, so 3rd line here above appears to describe a landing happening at right time but in wrong date.
Declared sources for Horizons data:
are we missing something?!?
CODE
Trajectory files Start (TDB) End (TDB)
-------------------------------------- ----------------- -----------------
od002_v1.V0.1 2018-May-05 12:39 2018-May-05 21:00
od037_v1_delTCAL.V0.1 2018-May-05 21:00 2018-Jun-08 00:00
od092_v1.V0.1 2018-Jun-08 00:00 2018-Jul-29 00:01
od102_v1.V0.1 2018-Jul-29 00:01 2018-Nov-25 19:40
4day_landed.V0.1 2018-Nov-25 19:40 2018-Nov-29 19:40
-------------------------------------- ----------------- -----------------
od002_v1.V0.1 2018-May-05 12:39 2018-May-05 21:00
od037_v1_delTCAL.V0.1 2018-May-05 21:00 2018-Jun-08 00:00
od092_v1.V0.1 2018-Jun-08 00:00 2018-Jul-29 00:01
od102_v1.V0.1 2018-Jul-29 00:01 2018-Nov-25 19:40
4day_landed.V0.1 2018-Nov-25 19:40 2018-Nov-29 19:40
are we missing something?!?
Simulator is eventually finished: I cleaned it up, added official Twitter feed, NASA live video and descriptions for all phases.
http://win98.altervista.org/space/explorat...-simulator.html
http://win98.altervista.org/space/explorat...-simulator.html
QUOTE (mcmcmc @ Nov 24 2018, 04:04 AM)
wouldn't you like to know in advance how your spaceship/spacecraft/aircraft/whatelse will be oriented during final descent? I would.
What point are you trying to make?
That we should be able to invent some impossible simulation technology in advance of EDL in complete defiance of chaos theory?
Or that a spacecraft swinging under a parachute should expend fuel unnecessarily to control it's attitude?
The vehicle knows it's attitude at the time, and conducts an appropriate heading change during the powered decent stage so it lands at the correct orientation. Phoenix executed the same EDL method well. I'd suggest reading several of the post landing reconstruction analysis papers such as this one http://citeseerx.ist.psu.edu/viewdoc/downl...p1&type=pdf
This landing system has no common heritage with ExoMars.
QUOTE (mcmcmc @ Nov 24 2018, 04:04 AM)
The point is: if you are going to land on Mars (not "generic you", but you nprev or djellison), wouldn't you like to know in advance how your spaceship/spacecraft/aircraft/whatelse will be oriented during final descent?
You need to calm down a little.
Certainly for previous landings there have been a lot of simulations of what the attitude on chute was, and we used them to calculate exposure times, photometric angles, etc, but at best they were measures of what could have happened. Nobody expected them to look much like reality, and they didn't. For example, the MSL descent was much less oscillatory than some of the simulations.
QUOTE (djellison @ Nov 24 2018, 04:33 PM)
I'd suggest reading several of the post landing reconstruction analysis papers such
Thanks, I've already read 6 of them: all complain about unexpainable terribly wrong data about attack angle after parachute deployment, and some of them presume that wind could be a possible cause, and the authors presume that radar could help fixing the data, but I was not able to find any EDL analysis report taking into account radar data.
Note that they don't say that this is a critical point; they just say that "nothing is known about spacecraft attitude between parachute jettisoning and landing, but it's evident that it is good as spacecrafts usually land safely" (this sounds a little scary to me, being an engineer).
This is why I think that the parachute-to-landing phase design needs some improvements (currently it sounds like "hey, let's hope all goes fine, we can't do anything better here"). Instead, all other phases look very precisely designed against any possible Murphy attack.
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