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CX2SA > SATDIG 12.05.12 21:05l 868 Lines 30294 Bytes #999 (0) @ WW
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To : SATDIG@WW
Today's Topics:
1. Re: TACSAT 3 Question (Thomas Doyle)
2. Revised NASA TV Coverahe (Clint Bradford)
3. K9TSU/9 in EN53 5-12-12 (Vincent, K9TSU)
4. /m passes (Vincent, K9TSU)
5. TAPR PSR Digital Journal Spring 2012 Edition Now Available
(Mark Thompson)
6. Dayton Hamvention TAPR Digital Forum Schedule, Friday, May
18, 9:15 am - 11:15 am (Mark Thompson)
7. Re: TACSAT 3 Question (Paul Williamson)
8. AMSAT/TAPR Hamvention Banquet, Friday Evening, 5/18
(Mark Thompson)
9. ExoplanetSat CubeSat in Time Magazine (Trevor .)
10. Re: TACSAT 3 Question (Alan P. Biddle)
11. Aalto-1 CubeSat Groundstation video and Mission animation
(Trevor .)
12. Re: TACSAT 3 Question (Thomas Doyle)
----------------------------------------------------------------------
Message: 1
Date: Fri, 11 May 2012 14:59:51 -0500
From: Thomas Doyle <tomdoyle1948@xxxxx.xxx>
To: Robert McGwier <rwmcgwier@xxxxx.xxx>
Cc: "AMSAT-BB@xxxxx.xxxx <AMSAT-BB@xxxxx.xxx>
Subject: [amsat-bb] Re: TACSAT 3 Question
Message-ID:
<CAHnRQRJDq+m8YHhpkmezh_3fNj5x_eSYhEamjjUfk=zx8F=47w@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
Bob and Alan,
There must be a better way to detect re-entry than simply than throwing an
unhandled exception.
You guys seem to be the experts - any suggestions on how to do it ?
It seems to be related to the BSTAR drag value. Some say when the BSTAR
drag value gets "too high" the sat has re-entered or is about to re-enter.
The recent
chicken little contest peaked my interest in this topic. So far no one has
offered the
magic value for "too high". Not looking for the obvious answer - it is too
high when
SatPC32 throws an exception.
Paul Williamson's NASAWASH would be a good starting point. Check the keps
for
problems and errors before posting them. The tracking program could also
check for
the problem values. Neither of these would be difficult if the the value of
"too high" was
known. Would you have to look at the other elements or is BSTAR enough.
thanks,
W9KE tom....
On Fri, May 11, 2012 at 10:42 AM, Robert McGwier <rwmcgwier@xxxxx.xxx>wrote:
> You mean other than that it has reentered?
>
> On Friday, May 11, 2012, Thomas Doyle wrote:
>
>> Is anyone else if having trouble with 'TACSAT 3'
>> When I try to track it with SATPC32 it throws an error.
>> The error message is in German.
>>
>> thanks W9KE tom ...
>> _______________________________________________
>> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
>> Not an AMSAT-NA member? Join now to support the amateur satellite program!
>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>>
>
>
> --
> Bob McGwier
> Facebook: N4HYBob
> ARS: N4HY
>
>
>
--
Sent from my computer.
tom ...
------------------------------
Message: 2
Date: Fri, 11 May 2012 14:08:58 -0700
From: Clint Bradford <clintbradford@xxx.xxx>
To: AMSAT BB <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Revised NASA TV Coverahe
Message-ID: <8B07DD8C-434B-4864-B93B-FD1CCCAAA3B6@xxx.xxx>
Content-Type: text/plain; CHARSET=US-ASCII
MEDIA ADVISORY: M12-084
UPDATED COVERAGE FOR NASA/SPACEX LAUNCH AND MISSION TO STATION
CAPE CANAVERAL, Fla. -- The second SpaceX demonstration launch for
NASA's Commercial Orbital Transportation Services (COTS) has been
rescheduled for a liftoff on Saturday, May 19. The launch of the
Falcon 9 rocket carrying a Dragon capsule will occur from Space
Launch Complex 40 at the Cape Canaveral Air Force Station in Florida.
There is a single instantaneous launch opportunity at 4:55 a.m. EDT.
NASA Television launch commentary from Cape Canaveral begins at 3:30
a.m.
During the flight, SpaceX's Dragon capsule will conduct a series of
check-out procedures to test and prove its systems, including the
capability to rendezvous and berth with the International Space
Station (ISS). The primary objectives for the flight include a flyby
of the space station at a distance of approximately 1.5 miles to
validate the operation of sensors and flight systems necessary for a
safe rendezvous and approach.
The spacecraft also will demonstrate the ability to abort the
rendezvous. Once these capabilities are successfully proven, the
Dragon will be cleared to berth with the space station.
FALCON 9 LAUNCH PAD PHOTO OPPORTUNITY
Friday, May 18 (L-1 day): A photo opportunity of the Falcon 9 rocket
and Dragon capsule on the launch pad will be available for the news
media. Spokespeople from SpaceX will be available to answer
questions.
Media will depart from NASA's Kennedy Space Center Press Site by
government bus at 9 a.m. for Space Launch Complex 40. Media will be
returned at approximately 11 a.m. SpaceX security regulations require
that media attending this event be U.S. citizens.
REMOTE CAMERA SETUPS
Friday, May 18 (L-1 day): Media will be able to establish
sound-activated remote cameras at the launch pad. The location is
within Space Launch Complex 40 on the east side of the pad inside the
perimeter fence. Media who want to participate in remote camera setup
will depart from Kennedy's Press Site by government bus at 9 a.m. in
association with the launch pad photo opportunity and will be
returned to the press site separately after remote camera set-up is
complete. SpaceX security regulations require that media
participating in this activity be U.S. citizens.
PRELAUNCH AND POST-LAUNCH NEWS CONFERENCES
Friday, May 18 (L-1 day): The prelaunch news conference for the
NASA/SpaceX launch will be held at the Kennedy Press Site at 1 p.m.
NASA Television will provide live and streaming Internet coverage.
Participants in the prelaunch news conference will be:
- Phil McAlister, Acting Director, NASA Commercial Spaceflight
Development
- Alan Lindenmoyer, Manager, NASA Commercial Crew and Cargo Program
- Gwynne Shotwell, President, SpaceX
- Joel Tumbiolo, Launch Weather Officer, 45th Weather Squadron, Cape
Canaveral Air Force Station
Media representatives can participate in the news conference in-person
at Kennedy or via a phone bridge by calling NASA's Johnson Space
Center newsroom at 12:45 p.m. at 281-483-5111.
Saturday, May 19 (Launch day):A postlaunch news conference will be
held at Kennedy's Press Site at approximately 8:30 a.m.
Audio of the launch and the prelaunch and postlaunch news conferences
also will be carried on the NASA "V" circuits, directly accessible by
dialing 321-867-1220, 1240, 1260 or 7135. The briefings will be
streamed live on the agency's website.
Saturday, May 19 (Launch day): A delegation from the Student
Spaceflight Experiments Program (SSEP) will be at the Kennedy Press
Site and available for interviews and experiment demonstrations
between 3 and 4:30 a.m. The students represent three of the
experiments that will launch aboard the SpaceX Dragon as part of the
International Space Station NanoRacks 9 platform. A sign-up sheet
will be available in the newsroom for those media representatives
wanting to talk to the students.
For information on the Student Spaceflight Experiments Program:
http://go.nasa.gov/INLqjT
NASA TV LAUNCH COVERAGE
Saturday, May 19 (Launch day): NASA TV live coverage begins at 3:30
a.m. and concludes at approximately 5:30 a.m.
On launch day, "mission audio," the launch conductor's countdown
activities without NASA TV launch commentary, will be carried on
321-867-7135 starting at 8 a.m. Launch information also will be
available on local amateur VHF radio frequency 146.940 MHz, heard
within Brevard County.
NASA TV MISSION COVERAGE
Monday, May 21 (Flight Day 3): Live coverage from NASA's Johnson Space
Center mission control in Houston as the Dragon spacecraft performs
its flyby of ISS to test its systems begins at 2:30 a.m. and will
continue until the Dragon passes out of the vicinity of the station.
A news briefing will be held following the activities.
Tuesday, May 22 (Flight Day 4): Live coverage of the rendezvous and
berthing of the Dragon spacecraft to the station begins at 2 a.m. and
will continue through the capture and berthing of the Dragon to the
station's Harmony node. A news briefing will be held once Dragon is
secured to the ISS.
Wednesday, May 23: Live coverage of the hatch opening and entry of the
Dragon spacecraft begins at 6 a.m. and will include a ceremony during
which the ISS crew will mark the occasion.
Johnson also will provide live coverage of the departure and reentry
of the Dragon spacecraft once a date is determined.
NEWS MEDIA LAUNCH VIEWING
Saturday, May 19 (Launch day): News media may view the launch from the
Kennedy Press Site. A sign-up sheet will be available in the newsroom
for those media representatives wanting to cover the launch from the
NASA Causeway or from the roof of the Complex 39 Launch Control
Center. These are primarily photo locations as there are no
facilities available. Buses will depart from the Press Site parking
lot at 3:30 a.m.
KENNEDY MEDIA CREDENTIALING
Media who want to attend the prelaunch events, including the prelaunch
news conference and launch, may request accreditation online at:
https://media.ksc.nasa.gov
The deadline for U.S. media to apply for launch accreditation is
May16. The deadline for international media to apply has passed.
Journalists who have already been approved for accreditation do not
need to reapply.
The Gate 2 Pass and Identification Building on State Road 3, Merritt
Island, will be open to pick up press credentials on the following
schedule:
Thursday, May 17: noon - 4 p.m.
Friday, May 18: 7 a.m. - 4 p.m.
Saturday, May 19: 1:30 - 4 a.m.
News media credentials will be valid for mission activities from
launch through splashdown at both the Kennedy Space Center and
Johnson Space Center.
KENNEDY PRESS SITE - HOURS OF OPERATION
Thursday, May 17: 8 a.m. - 4:30 p.m.
Friday, May 18: 8 a.m. - 4:30 p.m.
Saturday, May 19: 1 - 10:30 a.m.
Media badges will be valid for access to the Kennedy Press Site
through Gate 2 on State Road 3 on Merritt Island and Gate 3 on State
Road 405, located east of the Kennedy Space Center Visitor Complex.
On launch day, only Gate 3 will be open, which also can be accessed
from State Road 3 via Space Commerce Way.
For further information about media accreditation, contact Jennifer
Horner at 321-867-6598.
For more information about the NASA/SpaceX launch, contact the Kennedy
Press Site at 321-867-2468 or visit:
http://www.nasa.gov/kennedy
JOHNSON MEDIA ACCREDITATION
Media who are credentialed with badges at Kennedy for launch
activities will have their badges honored at Johnson for the duration
of the SpaceX mission. Please contact the Johnson newsroom for work
space information.
International media wanting access only to Johnson must submit the
required documentation for badging by Monday, May 14. U.S. media
wanting access only to Johnson must submit a request for badging by
Friday, May 18. Media who have already been approved for
accreditation do not need to reapply.
For mission information, contact the Johnson newsroom at 281-483-5111
or visit:
http://www.nasa.gov/johnson
For NASA TV downlink information, schedules and links to streaming
video, visit:
http://www.nasa.gov/ntv
For up-to-date SpaceX mission information and a schedule of NASA TV
coverage, visit:
http://www.nasa.gov/spacex
-end-
Clint Bradford
clintbradford@xxx.xxx
------------------------------
Message: 3
Date: Fri, 11 May 2012 22:20:53 -0500
From: "Vincent, K9TSU" <k9tsu@xxxxxxx.xxx>
To: "rod tds.net" <rod@xxx.xxx>, amsat-bb@xxxxx.xxx
Subject: [amsat-bb] K9TSU/9 in EN53 5-12-12
Message-ID:
<CAP4t4uSDDE72W-E=u315b=Nak18hdDwk3oCymOvwHx+7jsr-jA@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
Fellow sat-talkers!
I will be mobile and portable on all possible AO-27 passes and SO-50 passes
in EN53 tomorrow! Keep an eye on the bulletin board for the passes I plan
to make!
K9TSU
--
*Vince Waelti, K9TSU*
WX9MCS/R Control Operator
Midwest SSTRC Spotter # MW314
Green County ARES/SKYWARN
Winnebago County ARES/SKYWARN
------------------------------
Message: 4
Date: Fri, 11 May 2012 22:26:48 -0500
From: "Vincent, K9TSU" <k9tsu@xxxxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] /m passes
Message-ID:
<CAP4t4uRhf-Er8+bTvv-W63F+0K87kuiPsUWf3qBVgQSHX4QGCA@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
See the last email for more details. I will try my best to be on the 13:25
CENTRAL time pass of AO-27 and the 15:05 central pass.
--
*Vince Waelti, K9TSU*
WX9MCS/R Control Operator
Midwest SSTRC Spotter # MW314
Green County ARES/SKYWARN
Winnebago County ARES/SKYWARN
------------------------------
Message: 5
Date: Fri, 11 May 2012 22:07:16 -0700 (PDT)
From: Mark Thompson <wb9qzb_groups@xxxxx.xxx>
To: "APRS@xxxxxxxxxxx.xxxx <APRS@xxxxxxxxxxx.xxx>
Cc: "amsat-bb@xxxxx.xxxx <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] TAPR PSR Digital Journal Spring 2012 Edition Now
Available
Message-ID:
<1336799236.79588.YahooMailNeo@xxxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
TAPR PSR Digital Journal
Spring 2012 Edition Now Available
http://www.tapr.org/psr/psr118.pdf
------------------------------
Message: 6
Date: Fri, 11 May 2012 22:08:35 -0700 (PDT)
From: Mark Thompson <wb9qzb_groups@xxxxx.xxx>
To: "APRS@xxxxxxxxxxx.xxxx <APRS@xxxxxxxxxxx.xxx>
Cc: "amsat-bb@xxxxx.xxxx <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Dayton Hamvention TAPR Digital Forum Schedule,
Friday, May 18, 9:15 am - 11:15 am
Message-ID:
<1336799315.49634.YahooMailNeo@xxxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=utf-8
www.tapr.org/dayton.html#forum
Dayton Hamvention TAPR Digital Forum Schedule
When: Fri, May 18, 9:15 am ? 11:15 am
Where: Room 1
9:15 am
Introduction and TAPR Update
Steve Bible, N7HPR
9:25 am
Beyond open HPSDR: Hermes and the Future
Scotty Cowling, WA2DFI
9:50 am
Embedded DSP for PC-less SD
Lyle Johnson, KK7P
10:15 am
Time and Frequency Update
John Ackermann, N8UR
10:45 am
CODEC2
David Rowe, VK5DGR
------------------------------
Message: 7
Date: Sat, 12 May 2012 01:16:38 -0700
From: Paul Williamson <kb5mu@xxxxx.xxx>
To: Thomas Doyle <tomdoyle1948@xxxxx.xxx>
Cc: "AMSAT-BB@xxxxx.xxxx <AMSAT-BB@xxxxx.xxx>
Subject: [amsat-bb] Re: TACSAT 3 Question
Message-ID: <0FD2B963-52F3-4065-A68F-5F7ACFCA66AB@xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
On May 11, 2012, at 12:59 PM, Thomas Doyle wrote:
> There must be a better way to detect re-entry than simply than throwing an
> unhandled exception.
>
> You guys seem to be the experts - any suggestions on how to do it ?
> It seems to be related to the BSTAR drag value. Some say when the BSTAR
> drag value gets "too high" the sat has re-entered or is about to re-enter.
I don't have access to SatPC32 internals, but most amateur tracking programs
ignore BSTAR completely. BSTAR doesn't even appear in the so-called AMSAT
format element sets. It might not be the element you're looking for.
Mean motion, the number of revolutions the satellite makes per day, is a
nice simple value to look at to detect re-entry, but you can't just look at
the mean motion in the element set. That value, like all the other values in
the element set, is a snapshot as of the epoch time. Mean motion is actually
changing all the time, and we model that change rather simplistically as
linear. The value called "Decay rate" in the AMSAT format is basically the
rate of change of the mean motion, revolutions per day per day. To compute
the value of mean motion at the present (or target) time, you have to
multiply the decay rate by the time (in days) elapsed since the epoch time
of the element set, and add that to the mean motion from the element set.
The threshold to compare against would be the mean motion (number of
revolutions per day) of a satellite in circular orbit on the threshold of
re-entry. This would be somewhere between 16 revs/day (the familiar
90-minute orbit approximation) and about 17 revs/day (the mean motion a
satellite would have if orbiting at sea level).
For TACSAT-3 as shown in the current Keplerian elements bulletin, today (day
133 of 2012):
16.45 + (133-121.7) * 0.152 = 18.17
a clearly subterranean mean motion. If you compare TACSAT-3's values to
those of other satellites in the bulletin, you'll see that both mean motion
(16.45) and decay rate (0.15) are outliers, much higher than any of the
others.
It might or might not make sense to add a filter like that to a program like
NASAWASH. The element set is not invalid in itself. It's just invalid if
propagated to the present time.
I know I've glossed over a few details in the above analysis. I'm sure one
of the experts who actually understands orbital mechanics will correct me if
I've fouled it up entirely.
73 -Paul
kb5mu@xxxxx.xxx
------------------------------
Message: 8
Date: Fri, 11 May 2012 22:17:22 -0700 (PDT)
From: Mark Thompson <wb9qzb_groups@xxxxx.xxx>
To: "hamvention@xxxxxxxxxxx.xxxx <hamvention@xxxxxxxxxxx.xxx>,
"Ohiodigital@xxxxxxxxxxx.xxxx <Ohiodigital@xxxxxxxxxxx.xxx>
Cc: "hpsdr@xxxxx.xxxxxxxxx.xxxx <hpsdr@xxxxx.xxxxxxxxx.xxx>,
"DigitalModes@xxxxxxxxxxx.xxxx <DigitalModes@xxxxxxxxxxx.xxx>,
"D-STAR_23cm@xxxxxxxxxxx.xxxx <D-STAR_23cm@xxxxxxxxxxx.xxx>,
"amsat-bb@xxxxx.xxxx <amsat-bb@xxxxx.xxx>,
"soft_radio@xxxxxxxxxxx.xxxx <soft_radio@xxxxxxxxxxx.xxx>,
"APRS@xxxxxxxxxxx.xxxx <APRS@xxxxxxxxxxx.xxx>,
"DigitalATV@xxxxxxxxxxx.xxxx <DigitalATV@xxxxxxxxxxx.xxx>,
"SDRlist@xxxxxxxxxxx.xxxx <SDRlist@xxxxxxxxxxx.xxx>,
"digitalradio@xxxxxxxxxxx.xxxx <digitalradio@xxxxxxxxxxx.xxx>
Subject: [amsat-bb] AMSAT/TAPR Hamvention Banquet, Friday Evening,
5/18
Message-ID:
<1336799842.82401.YahooMailNeo@xxxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=iso-8859-1
http://www.amsat.org/amsat-new/hamvention/2012/Banquet.php
2012 AMSAT/TAPR Hamvention Banquet
The?sixth annual joint AMSAT/TAPR Banquet will be held Friday evening, May
18, 2012 during the Dayton Hamvention.
The Banquet will be at the:
Kohler Presidental Banquet Center
4572 Presidential Way
Kettering, OH 45429
(just south of Dayton).
Reservations are required and must be made by Monday,?14 May 2012 . Seating
is limited, so make your reservations early.
The
price for the Banquet is $30 per person. Reserved tickets may be picked
up at the AMSAT booth at Hamvention on Friday, or at the door.
You
may make reservations for the 2012 AMSAT/TAPR Banquet online in the
AMSAT Store.
AMSAT Presidents Club Gold members should let Martha know
if they are planning to attend the banquet.
Reserved tickets can be
picked up at the AMSAT booth on Friday or at the door to the Banquet.
For additional information contact Martha at the AMSAT office
(martha@xxxxx.xxxx.
Banquet Schedule
6:30 PM Doors open and Cash bar is available with Beer, Wine, Liquor and
soft drinks.
7:15 PM Buffet Dinner service begins. The Center has a justly deserved
reputation for good food and service.
8:15 Presentation by Howard Long, G6LVB, talking about his FUNcube Dongle,
the 64 - 1700 MHz Software Defined Receiver.
------------------------------
Message: 9
Date: Sat, 12 May 2012 12:09:38 +0100 (BST)
From: "Trevor ." <m5aka@xxxxx.xx.xx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] ExoplanetSat CubeSat in Time Magazine
Message-ID:
<1336820978.77190.YahooMailClassic@xxxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=utf-8
See http://www.uk.amsat.org/7348
73 Trevor M5AKA
------------------------------
Message: 10
Date: Sat, 12 May 2012 07:41:53 -0500
From: "Alan P. Biddle" <APBIDDLE@xxxxxx.xxx>
To: "'Thomas Doyle'" <tomdoyle1948@xxxxx.xxx>
Cc: AMSAT-BB@xxxxx.xxx
Subject: [amsat-bb] Re: TACSAT 3 Question
Message-ID: <C5C8557D9FEB44BD94A5F081266E6A28@xxxxxx>
Content-Type: text/plain; charset="us-ascii"
Tom,
As usual, Paul has covered the important points. I would suggest, if you
are really interested, getting an account on Space Track and looking at the
archived values for TLE of decayed satellites. Looking at the decay rate
will clearly give you an indication to within a day or so. Normally it is a
value of something like .00000X, but in the final days that number increases
rapidly. Empirically, when it gets close .01 the end is near, and the last
data always shows something like the .15 Paul mentioned. Alternatively, if
you are willing to look at two Keps, you can calculate the actual descent
rate. I recall ARISSat-1 was descending at something like 20km/orbit at the
end. I expect that if you pick 5-10 satellites and study the results, more
detailed criteria will suggest themselves. There is no doubt a good AMSAT
Journal article here.
>From the ARISSat-1 Chicken Little contest, I learned that there are already
many predictive models, but it should be relatively easy to decide from
current Keps when the satellite is down. For my own use, I usually know
from reports the status of any satellites which interest me. If a tracking
program throws an exception, I check Space Track for recently decayed
satellites, and here to see if there was a glitch in the Keps.
73s and have fun,
Alan
WA4SCA
-----Original Message-----
From: amsat-bb-bounces@xxxxx.xxx [mailto:amsat-bb-bounces@xxxxx.xxxx On
Behalf Of Paul Williamson
Sent: Saturday, May 12, 2012 3:17 AM
To: Thomas Doyle
Cc: AMSAT-BB@xxxxx.xxx
Subject: [amsat-bb] Re: TACSAT 3 Question
On May 11, 2012, at 12:59 PM, Thomas Doyle wrote:
> There must be a better way to detect re-entry than simply than throwing an
> unhandled exception.
>
> You guys seem to be the experts - any suggestions on how to do it ?
> It seems to be related to the BSTAR drag value. Some say when the BSTAR
> drag value gets "too high" the sat has re-entered or is about to re-enter.
I don't have access to SatPC32 internals, but most amateur tracking programs
ignore BSTAR completely. BSTAR doesn't even appear in the so-called AMSAT
format element sets. It might not be the element you're looking for.
Mean motion, the number of revolutions the satellite makes per day, is a
nice simple value to look at to detect re-entry, but you can't just look at
the mean motion in the element set. That value, like all the other values in
the element set, is a snapshot as of the epoch time. Mean motion is actually
changing all the time, and we model that change rather simplistically as
linear. The value called "Decay rate" in the AMSAT format is basically the
rate of change of the mean motion, revolutions per day per day. To compute
the value of mean motion at the present (or target) time, you have to
multiply the decay rate by the time (in days) elapsed since the epoch time
of the element set, and add that to the mean motion from the element set.
The threshold to compare against would be the mean motion (number of
revolutions per day) of a satellite in circular orbit on the threshold of
re-entry. This would be somewhere between 16 revs/day (the familiar
90-minute orbit approximation) and about 17 revs/day (the mean motion a
satellite would have if orbiting at sea level).
For TACSAT-3 as shown in the current Keplerian elements bulletin, today (day
133 of 2012):
16.45 + (133-121.7) * 0.152 = 18.17
a clearly subterranean mean motion. If you compare TACSAT-3's values to
those of other satellites in the bulletin, you'll see that both mean motion
(16.45) and decay rate (0.15) are outliers, much higher than any of the
others.
It might or might not make sense to add a filter like that to a program like
NASAWASH. The element set is not invalid in itself. It's just invalid if
propagated to the present time.
I know I've glossed over a few details in the above analysis. I'm sure one
of the experts who actually understands orbital mechanics will correct me if
I've fouled it up entirely.
73 -Paul
kb5mu@xxxxx.xxx
_______________________________________________
Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 11
Date: Sat, 12 May 2012 15:21:21 +0100 (BST)
From: "Trevor ." <m5aka@xxxxx.xx.xx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Aalto-1 CubeSat Groundstation video and Mission
animation
Message-ID:
<1336832481.17856.YahooMailClassic@xxxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=utf-8
Two videos, one of the Aalto-1 groundstation the other an animation of the
mission.
See http://www.uk.amsat.org/7371
73 Trevor M5AKA
------------------------------
Message: 12
Date: Sat, 12 May 2012 12:19:54 -0500
From: Thomas Doyle <tomdoyle1948@xxxxx.xxx>
To: APBIDDLE@xxxxxxx.xxx
Cc: AMSAT-BB@xxxxx.xxx
Subject: [amsat-bb] Re: TACSAT 3 Question
Message-ID:
<CAHnRQRLG+xkMTFKk-W7=9nxToK87XSC8Esi=uFqwAfOw0GzOYQ@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
One of the great things about AMSAT is the willingness of people like Alan
and Paul
to share information and answer questions. I followed Alan's chicken-little
contest and recall someone had done some graphs related to the decay. I
tried
searching for the postings but could not find them or remember who posted
them.
These days remembering what I had for breakfast is an occasion worthy of
celebration.
If anyone is willing to share their chicken-little contest secrets I would
be most interested
and appreciative.
73 W9KE tom...
On Sat, May 12, 2012 at 7:41 AM, Alan P. Biddle <APBIDDLE@xxxxxx.xxx> wrote:
> Tom,
>
> As usual, Paul has covered the important points. I would suggest, if you
> are really interested, getting an account on Space Track and looking at the
> archived values for TLE of decayed satellites. Looking at the decay rate
> will clearly give you an indication to within a day or so. Normally it is
> a
> value of something like .00000X, but in the final days that number
> increases
> rapidly. Empirically, when it gets close .01 the end is near, and the last
> data always shows something like the .15 Paul mentioned. Alternatively, if
> you are willing to look at two Keps, you can calculate the actual descent
> rate. I recall ARISSat-1 was descending at something like 20km/orbit at
> the
> end. I expect that if you pick 5-10 satellites and study the results, more
> detailed criteria will suggest themselves. There is no doubt a good AMSAT
> Journal article here.
>
> From the ARISSat-1 Chicken Little contest, I learned that there are already
> many predictive models, but it should be relatively easy to decide from
> current Keps when the satellite is down. For my own use, I usually know
> from reports the status of any satellites which interest me. If a tracking
> program throws an exception, I check Space Track for recently decayed
> satellites, and here to see if there was a glitch in the Keps.
>
> 73s and have fun,
>
> Alan
> WA4SCA
>
>
>
> -----Original Message-----
> From: amsat-bb-bounces@xxxxx.xxx [mailto:amsat-bb-bounces@xxxxx.xxxx On
> Behalf Of Paul Williamson
> Sent: Saturday, May 12, 2012 3:17 AM
> To: Thomas Doyle
> Cc: AMSAT-BB@xxxxx.xxx
> Subject: [amsat-bb] Re: TACSAT 3 Question
>
> On May 11, 2012, at 12:59 PM, Thomas Doyle wrote:
> > There must be a better way to detect re-entry than simply than throwing
> an
> > unhandled exception.
> >
> > You guys seem to be the experts - any suggestions on how to do it ?
> > It seems to be related to the BSTAR drag value. Some say when the BSTAR
> > drag value gets "too high" the sat has re-entered or is about to
> re-enter.
>
> I don't have access to SatPC32 internals, but most amateur tracking
> programs
> ignore BSTAR completely. BSTAR doesn't even appear in the so-called AMSAT
> format element sets. It might not be the element you're looking for.
>
> Mean motion, the number of revolutions the satellite makes per day, is a
> nice simple value to look at to detect re-entry, but you can't just look at
> the mean motion in the element set. That value, like all the other values
> in
> the element set, is a snapshot as of the epoch time. Mean motion is
> actually
> changing all the time, and we model that change rather simplistically as
> linear. The value called "Decay rate" in the AMSAT format is basically the
> rate of change of the mean motion, revolutions per day per day. To compute
> the value of mean motion at the present (or target) time, you have to
> multiply the decay rate by the time (in days) elapsed since the epoch time
> of the element set, and add that to the mean motion from the element set.
>
> The threshold to compare against would be the mean motion (number of
> revolutions per day) of a satellite in circular orbit on the threshold of
> re-entry. This would be somewhere between 16 revs/day (the familiar
> 90-minute orbit approximation) and about 17 revs/day (the mean motion a
> satellite would have if orbiting at sea level).
>
> For TACSAT-3 as shown in the current Keplerian elements bulletin, today
> (day
> 133 of 2012):
>
> 16.45 + (133-121.7) * 0.152 = 18.17
>
> a clearly subterranean mean motion. If you compare TACSAT-3's values to
> those of other satellites in the bulletin, you'll see that both mean motion
> (16.45) and decay rate (0.15) are outliers, much higher than any of the
> others.
>
> It might or might not make sense to add a filter like that to a program
> like
> NASAWASH. The element set is not invalid in itself. It's just invalid if
> propagated to the present time.
>
> I know I've glossed over a few details in the above analysis. I'm sure one
> of the experts who actually understands orbital mechanics will correct me
> if
> I've fouled it up entirely.
>
> 73 -Paul
> kb5mu@xxxxx.xxx
>
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
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>
>
>
>
--
Sent from my computer.
tom ...
------------------------------
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Sent via amsat-bb@xxxxx.xxx. Opinions expressed are those of the author.
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End of AMSAT-BB Digest, Vol 7, Issue 151
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