posted 01-07-2012 03:07 PM               

quote:

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Originally posted by dom:
David, you might have gotten off to a bad start with this story - if early analysis of its contents are to be believed.

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posted 01-08-2012 08:39 AM               

Yes I have seen the comments made by Jim Oberg. Criticism appears to focus on two issues: (first) the orbital position of the two spacecraft and the pre-selection of the orbital inclination; and (second) expressing incredulity that the US could have known the orbital inclination of Tiangong before it was launched (which was after X-37B).

On the former - of course the right-ascension influences exactly when they pass but the fact that they do pass each other is admitted and a matter of fact. The velocity of the flyby does not hinder electronic diagnosis of Tiangong and associated ground facilities in China and Africa and this latter aspect is the point.

There is a lot of activity going on across the surface of the globe within this orbital belt and there could be many reasons why X-37B has been placed in this highly unusual path.

Moreover, the orbit allows it to pass every four days over all China's domestic and foreign tracking stations which is inferred in the article.

On the latter criticism regarding the selection of the X-37B's orbit - all China's manned flights since 1999 have occupied precisely this path. I am greatly surprised that someone of Jim Oberg's high calibre and worthy reputation expresses astonishment that anyone should know beforehand that, when launched, Tiangong would be in that orbit.

Jim had not seen the article when he posted his statements and only asked me to send a copy after his views were out on the web. I ask all those making comment to read these two pages on the X-37B first.

I might also add that it has been a tradition of the BIS, and certainly Spaceflight magazine, to publish features trying to decipher the activities of both Russian and US intelligence gathering satellites during the Cold War. These articles were almost routine in Spaceflight but since the end of the Cold War that kind of analysis and speculation has been absent. It is in this tradition that the story was published.

Lastly, and most important, this story has nothing to do with 'pecuniary objectives' as some have claimed. I have no intention of using claimed sensationalism as a means of broadcasting the name of the magazine or the BIS with a view to recruiting subscriptions.

posted 01-08-2012 01:52 PM               

quote:

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Originally posted by dbaker:
I ask all those making comment to read these two pages on the X-37B first.

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posted 01-08-2012 05:40 PM               

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Originally posted by dbaker:
Yes I have seen the comments made by Jim Oberg.

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Mr. Baker does not appear to understand the basis of my objections at all, let me try to make the points clearer.

For point 1, he writes, "of course the right-ascension influences exactly when they pass but the fact that they do pass each other is admitted and a matter of fact." If Mr. Baker now is satisfied that the two vehicles are not and never will be co-planar, than this totally demolishes the significance he appears so enamored of - that the two inclinations happen to be very close. This demolition is caused by the fact that if criss-cross intercepts are all you are interested in [his new fall-back position, apparently], ANY two orbits of ANY plane will have exactly the same number - 2 per rev [so the coincidence of the orbital inclinations becomes moot].

Baker adds: "The velocity of the flyby does not hinder electronic diagnosis of Tiangong and associated ground facilities in China and Africa and this latter aspect is the point." Perhaps I need to study the original article further because I don't see the point. The undeniable ability of any space vehicle to carry out exactly such observations, from ANY low Earth orbit, totally dispels anything special about the X-37's orbit, and so the apparent central thesis of the article dissolves.

In fact, the very closeness of the orbital period of X-37 and Tiangong makes the former vehicle an extremely inconvenient observer of Tiangong, especially in light of the obvious requirements it be observed during specific short intervals of special activities, such as docking. This inconvenience is related to the repeatability of the close passes, which as with the synodic period of planets, is defined as the reciprocal of the difference of the reciprocals of the two orbiting objects. For current values this runs about ten days between repeat passes (a pair of close passes every ten days). During most of the rest of that period the X-37B actually remains totally out of line-of-sight of Tiangong, in one of the BLINDEST POSSIBLE orbits for observation, not hardly the BEST possible orbit.

For point 2, he writes that I "express[ed] incredulity that the US could have known the orbital inclination of Tiangong before it was launched (which was after X-37B)" This is an incorrect reading of my words leading to a misrepresentation of my objection. I expressed incredulity that the US could have predicted the orbital PLANE of Tiangong months before it was launched, not the orbital INCLINATION [it's possible some editor garbled this - I will check]. The plane depends both on the inclination, to be sure, as well as the Right Ascension of the Ascending Node, or RAAN. To achieve a co-planar orbit with Tiangong-1, which I surmised was the assertion of the to-appear article, would require prescience of a supernatural form to know the exact TIME it would be inserted into orbit, and hence define its RAAN.

I had suspected from my interpretation of the BBC article that Mr. Baker was not conversant in the significance of the RAAN in determining orbit-to-orbit accessibility, and this new misunderstanding only underscores my original concern about his understanding of orbital mechanics.

posted 01-09-2012 09:53 AM               

I have now read the as-published Spaceflight article and its technical argument is as unjustified as it originally looked, based on the second-hand BBC account [which was very professionally accurate].

The one-page article [no author], entitled "Is X-37B stalking China's space station?", describes the X-37B and Tiangong-1 as being "in almost exactly the same orbit", with the X-37B having "the ability to approach Tiangong-1 for diagnostic tracking and systems monitoring." [graf 1]. It then describes maneuvers by X-37B that "would bring it into a co-planar orbit with Tiangong-1." [graf 3]

The specific claim that the two vehicles are in the same orbit and co-planar is factually false.

The initial impressions of a 'horrendous' mistake in orbital mechanics are validated by the actual article.

By the way: An introduction to the article, by 'THE EDITOR' on page 1, actually endorses the theorized mission as prudent and justified, and applauds it.

posted 02-02-2012 12:02 PM               

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Originally posted by dbaker:
Cover story and four pages inside on MSL.

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posted 02-20-2012 05:29 AM               

Just go to bis-space.com, scroll down and click on Spaceflight News at the bottom of the front page to open current and archived features and comment.

Concerned at the lack of immediacy suffered by all print-magazines, news is being increasingly shifted to the web, as Spaceflight magazine gives more space to analysing the implications of the news rather than the announcement itself and to historical subjects.

posted 05-26-2012 04:59 AM               

A few years ago "Sky & Telescope" offered a 12 DVD-set to its readers, which has all magazines from 1942 to 2009 in scanned format.

posted 06-14-2012 01:13 AM               

There are plans to scan both the complete issues of ZENIT and ORBITER magazine which Astro published between 1984-1992. This is quite time consuming for small organizations. Perhaps the BIS could attempt the task in sections,such as by each decade?.

posted 06-17-2012 01:58 PM               

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Originally posted by ed zigoy:
In 2005 suggested the scanning of back issues idea to them twice, the BIS response, cold silence.

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posted 06-19-2012 09:54 AM               

Until now Spaceflight brought items which were nowhere else available although the internet age has changed things. Certainly something to be considered in the choice of aticles to be published. Nowadays "In Brief" section prints items widely available on the net.

Almost every issue of Spaceflight was worth keeping aside... otherwise I would only tear those "interesting" pages out for storage

posted 06-19-2012 02:06 PM               

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Originally posted by Philip:
Last year's index is available as a .pdf and was not printed in the December 2011 issue...

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posted 06-22-2012 03:28 PM               

The best other source was Countdown/Dixon Otto and this now "extinct" magazine has been digitized to PDF. AW&ST was focused on specifc technical areas, and as for popular press it was mostly fluff. STS Mission Profiles/Alan Fritsche was short lived 1992-1995, I believe.

So summing up, Spaceflight had the best general reporting of STS, with continuity.

I would be very much interested in seeing an archive in pdf - Even a compilation of the mission reports, perhaps an "STS Legacy DVD" would be of immense value.