My question is: Has there been any effort to improve or optimize the radiation patterns on the subsequent satellite navigation constellations (e.g. Glonass, Galileo, BeiDou-2) to facilitate trans-GEO navigation?

In a presentation entitled Enabling a Fully Interoperable GNSS Space Service Volume (slides 12, 24, 25, 26 are also shown below) some aspects of the possible use of GPS signals for navigation beyond Geosynchronous orbit are discussed.

While I have asked elsewhere about any actual navigation uses or tests of the GPS system, I am wondering now if this possibility was considered for other navigation constellations, e.g. Glonass, Galileo, or BeiDou-2.

Have the radiation patterns of the broadcast antennae on any of these satellite constellations been designed to provide additional power "over-the-limb" of the earth (see below)?

This answer has a great discussion (and nice plots!) of radiation patterns.

The AO-40 data show that the signals from the IIR Block satellites at large off-nadir angles are much larger than expected, and even at small angles are distinctly different than those of II and IIA Block satellites.

That suggests the possibility at least that the design was somehow modified to enhance the over-the-limb signal and improve the possibility of navigational use far from LEO.

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Space service volume (i.e. Altitudes above GPS) is a region of interest from all constellation providers. But the GNSS antenna main lobe coverage is limitedly very less. Efforts are being made in order to regulate the power levels available over the limb. As for as GPS is concerned the power levels will be moderated from the next generation of satellites GPS III update on GPS modernisationand it will be included Signal specification (targeting high altitude space users).

These plots are for GPS, but for other systems the antenna patterns are not available in detail. Only the main lobe antenna beam width angle is mentioned in some documents for other GNSS constellations.UNOOSA

When considering different frequency band to enable multi-GNSS navigation, L5 (frequency band from all constellation) has much wider range of antenna coverage than the primary FREQUENCY bands (such as L1)

Definitely CIS lunar space is region of interest but the power levels beyond GEO orbit is significantly low (-185dB @GEO) and this calls for the receiver capable to efficiently acquire and track weaker signals. NASA has already developed one receiver and flown it on the MMS mission @76,000 km. The results from the mission suggest that side lobes are more important above GPS constellation GPS Navigation Above 76,000 km for the MMS Mission.

There are also few feasibility studies on using GNSS navigation for Lunar transfer orbit Recent ones include Feasibility study of GNSS as navigation system to reach the Moon, Design of a High Sensitivity GNSS receiver for Lunar missions. There are several other studies which will give you idea on the requirements.

Hope it answers your question.

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  • $\begingroup$ These are really helpful links, thank you! Your answer is helpful - I haven't seen much of this - the Update on GPS Modernization... PDF is dated after my question was posted! However, my question is Has there been any effort to improve or optimize... subsequent constellations (e.g. Glonass, Galileo, BeiDou-2) and I asked this precisely because of what you've pointed out: "...for other systems the antenna patterns are not available in detail." Maybe there are simply statements somewhere indicating an "effort to improve or optimize" for those systems? $\endgroup$ – uhoh Oct 29 '16 at 1:01
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    $\begingroup$ As a precursor GPS is taking steps towards it. Other GNSS constellations will follow closely. Definitely other GNSS systems will works towards optimise their next generation of satellites. May be in coming months we get to know better from the next ICG Meeting on SSV. $\endgroup$ – akum Oct 29 '16 at 1:06
  • $\begingroup$ Because the idea of using GNSS off-planet (space service volume - thanks for the term!) is not new, I'm wondering if this capability was already considered and if the existing Glonass, Galileo, BeiDou-2 satellites already have some improvements to their radiation patterns for this purpose. $\endgroup$ – uhoh Oct 29 '16 at 1:16

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