Re: North Korea satellite: NOTAMs inconsistent with claimed sun-synchronous orbit

From: Brian Weeden (brian.weeden@gmail.com)
Date: Mon Apr 02 2012 - 12:26:24 UTC

• Next message: Ted Molczan: "RE: North Korea satellite: NOTAMs inconsistent with claimed sun-synchronous orbit"

```Figure 2 in this paper shows a plot of inclinations necessary for a
Sun-sync orbit at various altitudes (assuming zero eccentricity):
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/37900/1/04-0263.pdf

Ted, I agree with your overall point about the projected launch Az not
right for a SSO orbit at 500 km, but my math is coming out differently.
For a latitude of 39.66 and an Az of 192.3 I get an inclination of 99.44
degrees.  My excel formula for the inclination is

where B5 = latitude and B6 = Az

I think one of us may have a math error (likely me), so if someone could
check my formula I would appreciate it.

---------
Brian

On Mon, Apr 2, 2012 at 7:51 AM, David Tiller
<dtiller@captechconsulting.com>wrote:

> Ted,
>
> Thank you for your (as always) excellent analysis.
>
> It seems that there are two parameters that are used to compute the
> particulars of a sun-synchronous orbit - orbital altitude is used to derive
> the correct orbital inclination which then drives the launch azimuth based
> on latitude. Your analysis assumes that the stated launch altitude is
> correct and the launch azimuth is incorrect.
>
> What orbital altitude would be correct for a sun-synchronous orbit
> assuming that the launch azimuth will be as the DPRK stated?
>
> --
> David Tiller
> (804) 304-0638 | dtiller@captechconsulting.com
>
> ________________________________________
> From: seesat-l-bounces+dtiller=captechconsulting.com@satobs.org[seesat-l-bounces+dtiller=
> captechconsulting.com@satobs.org] on behalf of Ted Molczan [
> ssl3molcz@rogers.com]
> Sent: Sunday, April 01, 2012 10:46 PM
> To: seesat-l@satobs.org
> Subject: North Korea satellite: NOTAMs inconsistent with claimed
>  sun-synchronous orbit
>
> North Korea claims that its upcoming rocket launch will place a satellite
> in a 500 km, sun-synchronous orbit:
>
> http://www.kcna.co.jp/item/2012/201203/news28/20120328-40ee.html
>
> "It weighs 100kg and will circle along the solar synchronous orbit at
> 500km high altitude."
>
> The sun-synchronous claim is inconsistent with the NOTAM coordinates North
> Korea has issued for the impact zone of the
> rocket's two stages:
>
> NAVAREA  NO.12-0174       Date:2012/03/19 12 UTC
>
>  YELLOW SEA AND NORTH PACIFIC, LUZON.
>  ACCORDING TO INFORMATION FROM NORTH
>  KOREA VIA IMO, ROCKET LAUNCHING.
>  IMPACT HOUR 2200Z TO 0300Z COMMENCING
>  DAILY 11 TO 15 APR.
>  IMPACT AREAS BOUNDED BY
>  A. 35-12-25N 124-52-23E
>    35-12-13N 124-30-34E
>    35-55-20N 124-32-10E
>    35-55-10N 124-50-25E.
>  B. 15-08-19N 124-46-15E
>    15-09-35N 123-45-27E
>    19-24-32N 123-54-26E
>    19-23-08N 124-45-13E.
>  CANCEL THIS MSG 150400Z APR.
>
> Stage 1 would impact in zone A; stage 2 in zone B.
>
> The launch site is located at 39.660107 N, 124.705203 E.
>
> To be sun-synchronous, a 500 km orbit requires an inclination of 97.42
> deg. At the latitude of the launch site, a
> trajectory that directly ascends to that inclination requires a launch
> azimuth of approximately 192.3 deg (12.3 deg west
> of due south). The azimuth from the launch site through the various impact
> zones downrange should agree closely with
> this value, typically within a degree or so, absent any significant
> yaw-steering (aka dogleg) early in the ascent.
>
> The azimuth from the launch site to the midpoint of the southern boundary
> of the 2nd stage's impact zone (approx. 15.15
> N, 124.26 E) is 181.0 deg, which is far from the required 192.3 deg.
>
> I considered the possibility of an eastward dogleg early in the ascent,
> but the trajectory would have to turn toward
> approximately 192 deg azimuth well before the 2nd stage ceased firing, in
> which case the 2nd stage's impact zone should
> be oriented with its east and west sides pointing roughly toward azimuth
> 191 deg, but they do not. The west side points
> toward azimuth 181.8 deg, and the east side 179.8 deg - again far from the
> required value, and essentially identical to
> the azimuth calculated from the launch site. Therefore, there is no
> dogleg, which is not surprising, since it would
> involve overflying the Korean peninsula, probably including South Korea.
>
> I do not see how North Korea could reach a sun-synchronous orbit from the
> new launch site without risk to populated
> areas. Launching directly toward the required 192.3 deg azimuth would
> result in a trajectory that skirts China's east
> coast near Shanghai. The rocket's second stage would overfly Taiwan,
> before impacting in a zone bordering within perhaps
> 50 km of the west coast of the northern Philippines.
>
> To give a *very rough* idea of the effect of launching directly toward
> azimuth 192.3 deg, I have adjusted the longitudes
> of North Korea's NOTAMs:
>
>  A. 35-12-25N 123-42E
>    35-12-13N 123-20E
>    35-55-20N 123-33E
>    35-55-10N 123-51E
>  B. 15-08-19N 119-38E
>    15-09-35N 118-56E
>    19-24-32N 119-43E
>    19-23-08N 120-34E
>
> I very much doubt that North Korea plans for its rocket stages to fall in
> the zones I have estimated, but it is for
> North Korea to explain the inconsistency between the orbit it claims to be
> targeting and the NOTAMs it provided.
>
> Ted Molczan
>
>
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