Text 3358, 325 rader
Skriven 2009-12-05 22:30:18 av Amsat List (1:323/120.0)
Ärende: [ans] ANS-340 AMSAT Weekly Bulletin
=============================================
[ans] ANS-340 AMSAT Weekly Bulletin
AMSAT News Service Bulletin 340.01
From AMSAT HQ SILVER SPRING, MD.
December 6, 2009
To All RADIO AMATEURS
BID: $ANS-340.01
Since its launch AMSAT-Echo AO-51 has carried a spacecraft attitude
adjustment experiment which was tested for the first time this week.
The experiment contains a "reversible" magnet which will align the
spacecraft with Earth's magnetic field.
On the December 2, 2242 UTC pass of AO-51 AMSAT-NA VP Operations
Drew Glasbrenner, KO4MA issued the command to reverse the magnet
and "flip" the orientation of the satellite. The first effect of
the experiment was expected to be some changes in signal levels and
patterns. AO-51's 435 MHz downlink was expected to become slightly
weaker in the northern hemisphere and slightly stronger in the south-
ern hemisphere.
ZL2BX reported, "With two usable passes over ZL last night the most
notable feature was the frequent polarity shifts. Certainly good
strong signals but difficult to tell how it compares to previous
signal levels."
IW4DVZ reported results from a contact with EI8JB, "For me nothing
changed, I received from AO-51 the same strong signal as usual."
W6ZKH reported the only difference were frequent polarity changes. The
signal strength here on the West Coast seemed to be the same as before.
Tom Clark, K3IO offered an explanation for the received signal changes,
"Since angular momentum must be conserved when you "flip" the space-
craft it should precess (probably looking like tumbling) until the mom-
entum dampers absorb the change. Keep an eye on the solar panel currents
and I'll bet the spin rate will change."
Drew concluded, "We are still sifting through the telemetry, but as Tom
suggested in his email, the satellite is precessing (wobbling) quite
severely. This will calm down as the hysteresis rods do their job. Ini-
tial reports from Australia and New Zealand indicate stronger signals,
and about the same from South Africa. There are some peculiar things
about the magnetic field near South Africa, so that doesn't surprise me
too much, but is worth digging into once we get the whole orbit tele-
metry down."
The AO-51 Command Team appreciates any signal reports or observations
for the next few days that you can email to ao51-modes@amsat.org or
ko4ma@amsat.org. In a week or so the Command Team expects to re-orient
AO-51 back to its original attitude.
Twitter users can receive tweets from the AO-51 command team at
http://twitter.com/AMSAT or by adding "AMSAT" to your follow list.
[ANS thanks the AO-51 Command Team for the above information]
/EX
SB SAT @ AMSAT $ANS-340.02
OSCAR-11 REPORT 30 November 2009
[ans] ANS-340 AMSAT Weekly Bulletin
AMSAT News Service Bulletin 340.02
From AMSAT HQ SILVER SPRING, MD.
December 6, 2009
To All RADIO AMATEURS
BID: $ANS-340.02
This report covers the period from 21 April 2008 to 30 November 2009.
The satellite unexpectedly resumed transmissions recently. It was first
heard by Keith N4ZQ on 19 November 2009 and transmissions continued
until it switched OFF on 27 November. It was last heard by Tetsu JA0CAW
at 23:59 UTC 26 November 2009. Previously, it was last heard by Peter
ZL3TC on 23 April 2008, on a single pass.
Study of the satellite's behavior had suggested that its battery would
not sustain operation during solar eclipses, and the watchdog timer
would switch the satellite OFF after less than an orbit. Eclipses are
now occur during every orbit and will continue for many years. In
practice this meant that OSCAR-11 would only be heard occasionally by
stations monitoring the frequency while listening for other satellites.
During this period of inactivity the satellite achieved 25 years in
orbit on 01 March 2009. Congratulations to Professor Sir Martin
Sweeting, his team at the University of Surrey and participating amateur
radio groups, for this fine achievement.
Good signals have been received by stations located all over the world
during this recent period of activity and telemetry has been decoded
successfully. However, the satellite has only transmitted when in
sunlight. I have been overwhelmed by the number of reports received, too
many to list individually! Many thanks to everyone who sent email
reports or posted to AMSAT-BB.
The telemetry is unchanged from the 2008 downloads. The on-board clock
is now 241 days slow. When last received in 2008 it was 83 days slow.
The increasing error suggests that the clock may be stopping, when the
satellite is in eclipse.
The exact date when the satellite started transmitting is not known, so
if the watchdog timer was reset, the next transmissions might start
around 16 December, however if the timer went through its full operating
cycle, transmissions could resume around 06 December.
The Beacon frequencies are -
VHF 145.826 MHz. AFSK FM ASCII Telemetry
UHF 435.025 MHz. OFF
S-band 2401.5 MHz. OFF
The satellite is now subject to eclipses during every orbit. Long term
predictions indicate that eclipses will occur until 2019, when there will
be some eclipse free periods until 2023. However these very long term
predictions should be regarded with caution, as large tracking errors can
accumulate over long periods of time.
When telemetry was last received it showed that one of the solar arrays had
failed, and there was a large unexplained current drain on the main 14 volt
bus. After 25 years in orbit the battery has undergone over 100,000 partial
charge/discharge cycles, and observations suggest that it cannot power the
satellite during eclipses lasting more than about ten minutes, or
sometimes even during periods of poor solar attitude.
-------------
RECEPTION REPORTS REQUESTED!
Please send reception reports to xxxxx@amsat.org (replace xxxxx by
g3cwv) or post to amsat-bb. If you have a file, please let me know what
you have, before sending it!
The satellite transmits on 145.826 MHz., set receiver to NBFM. OSCAR-11
has a characteristic sound, rather like raspy slow morse code, sending
"di di dah dah dah dah dah dah dah" sent over five seconds. If you are
receiving a very weak signal, switch the receiver to CW or SSB. You
should hear several sidebands around the carrier frequency, should be
able to hear the characteristic 'morse code like' sound on at least one
sideband.
Please note that you need a clean noise free signal to decode the
signals. There is an audio clip on my OLD website
www.users.zetnet.co.uk/clivew/ which may be useful for identification
and as test signal for decoding.
-------------
The current status of the satellite, is that all the analogue telemetry
channels, 0 to 59 are zero, ie they have failed. The status channels 60 to
67 are still working. The real time clock is showing a large accumulated
error, although over short periods timekeeping is accurate to a few
seconds per month. When last heard the clock was 241 days slow. The
day of the month has a bit stuck at 'one' so the day of the month may show
an error of +40 days for some dates. The time display has switched into 12
hour mode. Unfortunately, there is no AM/PM indicator, since the time
display format was designed for 24 hour mode.
The spacecraft computer and active attitude control system have switched
OFF, ie. the satellite' attitude is controlled only by the passive gravity
boom gradient, and the satellite is free to spin at any speed.
The watchdog timer now operates on a 20 day cycle. The ON/OFF times have
tended to be very consistent. The average of many observations show this to
be 20.7 days, ie. 10.3 days ON followed by 10.4 days OFF. However, poor
solar attitude may result may result in a low 14 volt line supply, which
may cause the beacon to switch OFF prematurely, and reset the watchdog
timer cycle. When this occurs, the beacon is OFF for 20.7 days.
OSCAR-11 was the second satellite from the University of Surrey,
www.ee.surrey.ac.uk/SSC. It was designed, built and launched, within a
time scale of six months, by a team headed by Martin Sweeting G3YJO.
Amateur radio groups working at various locations in the world, also
contributed to the project. It used commercially available 'off the shelf'
components (COTS). Following the success of these satellites, in 1985
Surrey Satellite Technology Ltd. www.sstl.co.uk was formed, as a commercial
venture. This grew into a major company which has produced over 30 small
satellite projects for a global market.
The University of Surrey has recently sold it's major
shareholding in SSTL to EADS-Astrium. The joint company will therefore
have the experience of manufacturing large and small satellites, for
geo-synchronous and low earth orbits.
In regognition of his work, Martin G3YJO, was appointed Professor at the
University of Surrey. He received an OBE in the 1995 Queens birthday
honours list, and in 2002 a knighthood in the New Year's honours list.
Listeners to OSCAR-11 may be interested in visiting my websites. If you need
to know what OSCAR-11 should sound like, there is a short audio clip for
you to hear. The last telemetry received from the satellite is available
for download. The website contains an archive of news & telemetry data
which has now been updated. It also contains details about using a
soundcard or hardware demodulators for data capture. There is software for
capturing data, and decoding ASCII telemetry. The URL is
www.users.zetnet.co.uk/clivew/ However, please note that this site
is no longer being updated, and the latest news and information will and
will be uploaded to my new site www.g3cwv.co.uk which is currently
being constructed.
If you place this bulletin on a terrestrial packet network, please
use the bulletin identifier $BID:U2RPT145.CWV, to prevent duplication.
73 Clive G3CWV xxxxx@amsat.org (please replace xxxxx by g3cwv)
[ANS thanks Clive, G3CWV, for the above information]
/EX
SB SAT @ AMSAT $ANS-340.03
ARISS Status - 30 November 2009
[ans] ANS-340 AMSAT Weekly Bulletin
AMSAT News Service Bulletin 340.03
From AMSAT HQ SILVER SPRING, MD.
December 6, 2009
To All RADIO AMATEURS
BID: $ANS-340.03
1. De Winne Speaks with Dumbleyung Primary School through ARISS
On Thursday, November 26, Dumbleyung Primary School in Western Australia to=
ok
part in an Amateur Radio on the International =
Space Station (ARISS) contact with
Frank De Winne, ON1DWN via telebridge station VK4KHZ in Australia. To prepa=
re
for the contact, students studied Earth, its structure and the solar system=
. As
part of the ARISS event, students in Years 5 -7 gave presentations of their
space work and viewed footage of the ISS as well as video of an astronaut
interview. All 21 children had their questions answered during their radio
contact and ABC (Australian Broadcasting Corporation) News covered the even=
t.
2. Don Bosco Institut Experiences ARISS Contact
On Thursday, November 26, an Amateur Radio on the International Space Stati=
on
(ARISS) contact was held between Institut Don Bosco in Bruxelles, Belgium a=
nd
Frank De Winne on the ISS. The connection was made possible through telebri=
dge
station ON4ISS in Belgium. Students asked 19 questions of the astronaut dur=
ing
the ISS pass. Don Bosco is a secondary industrial technical school with an
enrollment of approximately 750 students and offers courses in carpentry,
electricity, mechanics, computing, printing and electronics.
3. ARISS Contact held with Katholieke Centrumscholen Sint-Truiden Students
Students attending Katholieke Centrumscholen Sint-Truiden in Sint-Truiden,
Belgium experienced a successful Amateur Radio on the International Space
Station (ARISS) contact with Frank De Winne on Thursday, November 26 via
telebridge station ON4ISS in Belgium. Twenty questions were asked and answe=
red.
In order to prepare for the radio contact, the students studied astronomy a=
nd
science. In addition, the school headmaster talked to the youth about the I=
SS
and his own experiences during two =93space camps=94 in the U.S. (Huntsvill=
e and
Kennedy Space Center).
4. ARRL Covers Installation of Columbus Module Antennas
The American Radio Relay League (ARRL) ran an article about the new antennas
that were installed on the Columbus module. To view the story, which ran in=
the
November 25 issue of the ARRL Letter, see:
https://www.arrl.org/arrlletter/index.html?issue=3D2009-11-25
5. ARISS News on Amateur Radio Newsline
On November 27, Amateur Radio Newsline Report 1685 reported on the new Colu=
mbus
module ARISS (Amateur Radio on the International =
Space Station) antenna. To view
=93Ham Radio in Space: ISS Gets New Dual Band Antenna,=94 see:
ftp://ftp.arnewsline.org/quincy/News/news.txt
6. New Web Site for ARISS-Brazil
ARISS Brazil recently formed a partnership with the internet portal Di=E1ri=
o da
Produ=E7=E3o.com to publicize ARISS activities in Brazil and South America.=
To view
the Web site, go to: http://diariodaproducao.com/
[ANS thanks Carol, KB3LKI, for the above information]
/EX
In addition to regular membership, AMSAT offers membership in the President=
's
Club. Members of the President's Club, as sustaining donors to AMSAT Project
Funds, will be eligible to receive additional benefits. Application forms a=
re
available from the AMSAT Office.
73,
This week's ANS Editor,
Lee McLamb, KU4OS
ku4os at amsat dot org
_______________________________________________
Via the ANS mailing list courtesy of AMSAT-NA
http://amsat.org/mailman/listinfo/ans
--- ViaMAIL!/WC v1.60d
* Origin: Chowdanet (401-724-4410) telnet://chowdanet.com (1:323/120)
|