||This is an index to several pages that were developed for
information and progress reports on the SCIGN radome project. The
development effort was completed in March 1999. A final report
on the development effort is available here . Since then the radomes
have been available from SCIGN - contact
John McRaney (213)740-5842 for pricing or to place orders.
Material reported below results from a SCIGN collaborative effort by
Ken Hudnut, John Galetzka,
Frank Wyatt and Stephen Dockter (and others as noted in pages below).
SCIGN Radome Project Index:
For more detailed historical footnotes, see the now-inactive Progress Log
4/30/2001 - Studies continue on attempts to understand the jumps observed by colleagues in
Iceland and British Columbia upon the introduction of SCIGN domes at field sites [see entry
below for 12/14/2000 (c)]. In this regard,
a new report entitled, "Remarks on the Effects of the SCIS Radome on PCV" has
been contributed by Martin Schmitz and Gerhard Wubbena of Geo++, Garbsen, Germany. This
available here in a 2.2 MB PDF file. They performed absolute Phase Center Variation
(PCV) field calibration tests using a Leica AT504 Dorne-Margolin Choke Ring (DMCR) antenna,
with and without the SCIGN short dome (IGS code SCIS). Their results indicate significant
shifts in vertical phase center, upon introduction of the SCIGN dome, at high elevation angles
[L1 up to 4 mm, L2 < 2 mm, and L0 (ionosphere-free linear combination) up to 12 mm].
They also comment that the high-elevation angle PCV dependency would imply an even
larger effect is possible due to satellite geometry at high latitudes, i.e., the "Northern Hole."
Also, here is
their web page describing further their calibration and test procedures.
The vertical phase center dependency with high elevation angle has been
previously reported by JPL, based on an earlier and different kind of testing. In
other news, an apparent station shift at SCIGN station BGIS (10 mm to south at 2000.63)
is now thought to have coincided
with vandals having smashed a hole in the side of the dome (and doing minor damage to
the antenna itself) with a brick. This damage was just discovered on a recent site visit
specifically to investigate this jump. We plan to conduct a test to see if the domes with
and without vandal-inflicted holes introduce phase center shifts (we suspect they do).
12/14/2000 (b) - Just a note to let you know that we've noticed a couple of things about the effects
of field conditions on the SCIGN domes. First, they tend to yellow slightly with prolonged sun
exposure. We have checked and this appears to only go skin deep - that is, it does not seem to
involve penetrative weathering of the domes. Also, the hand-written serial numbers on the outer
surfaces of the dome will come off after awhile, whereas the serial numbers written on the underside
of the base plate tend to last longer. We suggest possibly using an inscription/scribing tool
to scratch or engrave the serial number into the parts, if you wish. These were supposed to be
pad-printed (like the logo), and we're not surprised that the 'permanent' marker is wearing off.
12/14/2000 (c) - Colleagues Thora Arnadottir and Halldor Geirsson, at the Iceland GPS Network (ISGPS)
have reported an observed shift in apparent phase center vertical position when they installed
a SCIGN radome. This result is contained in their
Report on ISGPS, dated 6/15/00.
They have kindly prepared data distribution files so that others may also evaluate the same
data in order to test whether this jump is software dependent, etc. The data are available
here . Note that data from
the other ISGPS stations are also available on
the ISGPS main web site . Our colleagues Herb Dragert and others, at the
Geological Survey of Canada, Pacific Geoscience Centre,
in data from their
Western Canada Deformation Array (WCDA),
similarly observe vertical jumps
when they have introduced the SCIGN dome. Currently this is being studied because in
tests SCIGN conducted we saw no such jumps. Possibly higher latitude sites, or some
processing software issues, may provide an explanation eventually.
3/31/99 - Photo of station NOPK, which now has a new SCIGN adaptor, base plate
and tall radome mounted on it. Click on the photo for a larger version, or click
here for additional photos of the site.
Also, in anticipation of several orders we are now having MCA go ahead with making
jigs to perform secondary operations for mounting the short radome to antennas that
do not have the 12 threaded holes in their outermost choke ring (Trimble, AOA). See
the drawings numbered DSP-006-B and DSP-008-B on our
as-built drawings web page for additional details.
3/23/99 - 48 tall domes with base plates were successfully delivered to the SCIGN installation
contractor today. Also, the talk to be presented at the SCIGN annual meeting regarding the
SCIGN adaptors and radomes is now available here.
Instructions for assembly of the tall and the
short domes are also available on-line now.
3/12/99 - John McRaney has been sending out requests in order to anticipate and plan
for the next production run. Please
e-mail John McRaney, the SCIGN Network Administrator, for information if you
have not yet been contacted but wish to order some radomes (and/or SCIGN adaptors).
3/4/99 - We are now in production of the units for SCIGN. There will
be 250 of the tall units and 50 of the short units produced in this
initial production run.
12/30/98 - Testing of the first-article parts has been under way for
the past three weeks. Initial findings from tests on North Mudd, by the
SCIGN/USGS group, are reported
here. The Scripps and JPL groups have studied data from tests at PFO,
and the JPL findings are reported
here. So far, it appears from testing conducted by the USGS, Scripps, and JPL
groups that the radomes introduce less than 0.2 mm changes in horizontal phase
center and less than 2 mm changes in vertical phase center (when using normal
data processing parameters). The JPL group's analysis indicates that although
"...performance of the domed-antenna seems to match that of the
no-domed-antenna in repeatability, phase residuals, and elevation cutoff
dependence (within our standard operating range of 7-20 degrees),"
the radome does appear to introduce more than the usual amount of dependence on
change in vertical phase center at elevation angle cut-offs of greater than
about 20-25 degrees. Further analysis is
in progress and will be reported as results are available. Photographs of
the tall and short model radomes are also
12/4/98 - The first tall and short radome samples were delivered to SCIGN.
[All of the remaining first-article parts were delivered as of 12/10 and they
have now all been distributed within SCIGN and shipped out for testing by
11/25/98 - The first Xenoy 2730U prototypes were shot (in the wrong
color - too dark) and one unit was sectioned and wall thicknesses
measured by MCA. For comparison to the earlier thermoformed prototype
radomes, the accompanying figure
shows how much less wall thickness
variation we can expect to see in the injection molded radomes.
[On 12/3, we added these two plots for comparisons:
New radome and
Old radome showing
wall thickness variation in profile section of the radome wall].
Moreover, the injection molded parts should show very good repeatability
from part to part in whatever wall thickness variations do occur. In
contrast, thermoforming would have greater part to part variations.
11/4/98 - The ABS prototypes of the tall dome and base plate were
displayed for the first time at the IGS workshop
in Annapolis, Maryland this week. The poster
that accompanied these display models at the IGS workshop is available
to view here.
For a 3MB high resolution file of the poster, click
11/2/98 - The first shots (done in ABS to test the molds) were done last Friday (10/30/98).
Photographs of the action, along with brief explanatory captions, can be found
Here is a
photo showing water damage to the LNA cavity of the DMCR antenna that was deployed
at SCIGN station RTHS with no radome covering it. Water made its way into the cavity,
and slowly corroded the electronics. Disturbingly, this caused gradual degradation of
the GPS results from this station, rather than a sudden failure of the antenna (which
would have been obvious and more readily corrected). Although radomes do not ensure
that such gradual corrosion will never occur, they certainly make it much less likely.
The Progress Log has been separated
from this index page and moved to a new web page of its own.
It will be updated more frequently than this index page;
it is a listing of progress updates (roughly once per week now
that the project is in the hands of the injection molding company).
Also, outdated material is still
available for reference, but it has also been separated from
this index page.
Mold Filling and Packing Report by PSI: this is a
PowerPoint HTML document of the full contents of the report
provided to the SCIGN project by Polymer Solutions, Inc.
The PowerPoint file may be downloaded directly by clicking
here (Windows NT file).
Photographs related to the SCIGN radome project
last update March 31 at 12:40 p.m.
These reports are preliminary and have not been reviewed for
conformity with U. S. Geological Survey editorial standards.
Any use of trade, product, or firm names is for descriptive
use only and does not imply endorsement by the U. S. Government.
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