QZSS Michibiki set healthy for L1 C/A and L2C

First QZSS satellite Michibiki is set healthy for the L1 C/A and L2C.
L5, L1C and other advanced signals still pending technological
verification.

More details on JAXA site:
http://www.jaxa.jp/press/2011/06/20110622_michibiki_e.html

GPSWorld:
http://www.gpsworld.com/gnss-system/augmentation-assistance/news/qzss-satellite-michibiki-set-usable-first-naqu-issued-11817

Marcelo Pacheco

I'm curious how consumer GPS receivers will evolve. Certainly, the
two C/A code PRNs are no problem .. the data fields are retrieved
using existing GPS practice. The L2C is different matter as no
consumer devices exist. But, L2C can be made available from eight GPS
satellites on orbit. Perhaps we will see L2C receivers in Japan.

Will new designs initially implement L1C and L5 in anticipation of
their availability? I doubt they will.

a) QZS L1C isn't implemented in strict accordance with the US
specification but it's close enough that receiver software can
probably handle it as a special case. I don't know why QZS designed
it that way. I guess, for now, it doesn't matter because GPS won't be
sending L1C for many years.

b) The separation in frequency between L1 and L5 will complicate the
radio portion of a receiver. So I'm thinking the designers will forgo
L5 until several more GPS IIF satellites are operational.

--- CHAS

On 2011-06-25 12:14 , HIPAR wrote:

Market demand. Whether exiting GPS makers respond to or create the
demand is another issue.


The cellphone world has produced many innovative antenna packages, often
with many band segments on a single substrate. Likewise, and related,
automobile antenna packages have many bands in a small package (the ugly
antenna bump usually above the rear window).

I've seen an antenna design that uses fractal geometry to lay several
widely separate and various bandwidths all on the same, small surface.

Just a sec... ah, here:

http://en.wikipedia.org/wiki/Fractal_antenna

--
gmail originated posts filtered due to spam.

Didn't realize until CHAS's post that they were different.

http://qz-vision.jaxa.jp/USE/is-qzss/IS-QZSS_12_E.pdf

"8.1 Differences in Navigation Messages

The QZSS Navigation Messages for each signal (number of bits, scale
factor, parameter range, units)
are designed to preserve interoperability with GPS to the greatest
extent possible. However, based on
differences in the conditions unique to GPS and QZSS (QZS satellite
orbit conditions, etc.), in some
cases QZSS Navigation Messages cannot be expressed using the same
definitions as those for GPS.
Moreover, in order to provide QZSS with added value not present in
GPS, some content has been
intentionally defined differently from GPS. . . . "

One pretty straightforward difference is removing the max eccentricity
of 0.03.

Likewise, they change the nominal inclination in the almanac, from 0.3
to 0.25 semi-circle.

Some changes in RF characteristics also.

http://qzss.jaxa.jp/is-qzss/US-Japan_TWG_Statement_24May07Web_Version.pdf

""In order to better serve the GPS and QZSS commercial receiver
manufacturing market, GPS and QZSS have agreed to transmit nearly
identical L1 C/A, L1C, L2C, and L5 signals. The purpose of this TWG
statement is to document the cooperation, control, and publication of
the L1 C/A, L1C, L2C, and L5 GPS and QZSS signal definitions.

. . . An additional document, IS-QZSS identifies specific L1 C/A, L1C,
L2C, and L5 QZSS characteristics that are not included in the IS-
GPS-800, IS-GPS-705, and IS-GPS-200 baseline document. IS-QZSS is
controlled and managed by Japan.

Should either the GPS or QZSS programs consider modifying their signal
specifications, notification of such modifications is implemented
through either US-Japan Expert Working Group (EWG) or JAXA-GPS Systems
Wing channels as soon as possible."

The size of the West Asia/Pacific market will make QZSS L1 C/A a must,
specially it's just a software upgrade to be able to receive QZSS L1 C/
A.
L1C doesn't have much of an appeal for QZSS, since they already have
L1 C/A. L1C demand will come out of Galileo, since that's their only
signal in the L1 band.
L5 support will be driven by Galileo as well, since GPS should take
until circa 2025 to reach L5 IOC, with the need for another 17
launches to get there. Hopefully Galileo will have 18 operational
birds in the next 6 years. Even then, your average smartphone probably
won't have L5 or L2C support, only higher end equipment will get L5
support at first, I'd guess dedicated GPS equipment worth at least US$
1000. But L1C support shouldn't take long, with the urban canyon
scenario, adding Galileo support will make a huge difference in high
mask angle environments, where dual frequency doesn't help that much.
Perhaps standalone USB GPS sensors with L5 and/or L2C support might be
available at an affordable cost as well, due to their technical
simplicity. Aviation and High accuracy users will love it, since SBAS
+GPS+Galileo+L5 should result in sub-meter accuracy 100% of the time
with 18 Galileo + 12 IIF + SBAS L1/L5 ranging. In the QZSS coverage
area galileo+QZSS will make L5 fully useable for high accuracy with as
little as 18 galileo satellites.

Marcelo Pacheco