[Sls-ocm] Remarks on LEO downlinks

Wed Aug 25 06:28:24 EDT 2010

Dear All,

As Massimo requested, I modified the minutes of the last meeting
(Portsmouth):

http://cwe.ccsds.org/sls/docs/SLS-OCM/Meeting%20Materials/2010_05_Portsm
outh/SIG_OCM_20100825_MoM.pdf

by adding his following remarks on the topic "LEO downlinks: direct and
GEO-relay links":

i) The comparison (in term of throughput) between RF and optical LEO-GND
assumes 800Mbps for the RF link, while the comparison would better
consider the expected data rates using K band (26 GHz). During the
Spring meeting, ESA showed the expected average data rate in this band
would be above 1.3Gbps over a 540MHz channel adopting VCM techniques
(above 800Mbps without VCM), for a polar station (Svalbard). Considering
that the band can accomodate 2 such channels, more than 2.6Gbps average
data rate can be expected. So these figures may change the outlook of
the comparison RF vs optical. (Even though Optical with WDM would still
provide higher throughput, according to the figures provided). 

ii) The conclusion that "a direct LEO-GND is cheaper than a LEO-GEO-GND"
doesn't fully represent the situation in the relative short term (5-10
years), considering the current technical developments on LEO-GEO-GND
links (e.g. EDRS, Alphasat).

Regards

Nicolas

-- 

Nicolas Perlot, Ph.D. 

Digital Networks Section, 

Optical Communications Group 

German Aerospace Center (DLR)                 phone: ++49/8153/281836 

Institute of Communications and Navigation    fax:   ++49/8153/282844 

Oberpfaffenhofen, P.O. Box 11 16              email:
nicolas.perlot at dlr.de 

82234 Wessling, Germany
http://www.dlr.de/KN/KN-DN/

________________________________

From: Massimo.Bertinelli at esa.int [mailto:Massimo.Bertinelli at esa.int] 
Sent: Mittwoch, 18. August 2010 16:00
To: Perlot, Nicolas
Cc: sls-com at mailman.ccsds.org
Subject: RE: [Sls-ocm] Charter draft for OCM working goup

Dear Nicolas, 

thank you for your reply. 
For the sake of clarity, I would like to point out that, in my mail of
23.07, I was objecting to the minutes produced after the meeting, not to
the content of your presentation. 
I certainly don't ask to change the view of your Institution, as
contained in such presentation, whether I agree or not. 
Nevertheless, it would be fair that the moms reflect all the opinions
expressed during the meeting. 
The way they are now (as published in CWE), in my opinion, they don't
mirror the discussions we had. 
If you wish, I can certainly provide you with a summary of the points I
raised in Virginia Beach. 

Best regards, 
Massimo
---------------------------------------------------
Massimo Bertinelli
Communication Systems Engineer
ESA/Estec

Tel. +31 (0)71 5653435
-------------------------------------------------- 

From: 

<Nicolas.Perlot at dlr.de> 

To: 

<Massimo.Bertinelli at esa.int> 

Cc: 

<sls-com at mailman.ccsds.org>, <sls-com-bounces at mailman.ccsds.org> 

Date: 

09/08/2010 11:41 

Subject: 

RE: [Sls-ocm] Charter draft for OCM working goup

________________________________

Dear Massimo, 

1) I agree that we should have a completed version of the white paper as
soon as possible. 

2) As you suggested, I will add the following point on the agenda of the
Fall meeting (London): "Discussion on the participation of ESA to the
OCM work and on ESA internal approval process". 

3) About your objections during the Spring meeting: 
If I remember correctly, you objected during my presentation on direct
LEO downlinks that GEO satellites with optical payloads were already
flying (ARTEMIS) or about to fly (Alphasat, EDRS). J-L. Gerner also
mentioned the need for onboard memory for direct optical downlinks. I
agree. But these remarks do not change the view of my institute DLR-IKN
(and also my view) on direct LEO downlinks. What I was presenting was
the view of my institute DLR-IKN, just like JPL, NICT and JAXA presented
their views on optical links. If ESA has different views which you are
aware of, you are welcome to present them. 
So the document I presented was a DLR-IKN document supporting CCSDS
discussion, but it was not a CCSDS document. So it does not have to
contain your remarks. 

4)  I suggest to avoid the Post Scriptum in e-mails and to keep the
message content before the signature: I saw your P.S. only the second
time I read your message.  I recognize, though, the usefulness of P.S.
for paper letters. 

Regards, 
Nicolas 

Chair of OCM-SIG 

-- 
Nicolas Perlot, Ph.D. 
Digital Networks Section, 
Optical Communications Group 

German Aerospace Center (DLR)                 phone: ++49/8153/281836 
Institute of Communications and Navigation    fax:   ++49/8153/282844 
Oberpfaffenhofen, P.O. Box 11 16              email:
nicolas.perlot at dlr.de 
82234 Wessling, Germany
http://www.dlr.de/KN/KN-DN/ <http://www.dlr.de/KN/KN-DN/>  

________________________________

From: Massimo.Bertinelli at esa.int [mailto:Massimo.Bertinelli at esa.int
<mailto:Massimo.Bertinelli at esa.int> ] 
Sent: Freitag, 23. Juli 2010 15:12
To: Perlot, Nicolas
Cc: sls-com at mailman.ccsds.org; sls-com-bounces at mailman.ccsds.org
Subject: Re: [Sls-ocm] Charter draft for OCM working goup 

Dear Nicolas, 
thank you for the draft. 

As an ESA SIG member, it is my opinion that the creation of a new WG is
still premature, while the SIG should first finish the work it was
supposed to do. 
In particular, I believe that the SIG should finalize the white book on
"Optical coding and modulation". Eventually, once the material is more
mature, a Green Book may be delivered. 

In any case, some more time and supporting material will be necessary to
understand whether ESA can partecipate to the work, due to the internal
approval process. 
I would suggest coming back to this at the London meeting, after the
technical discussions are over. 

Best regards, 
Massimo 

P.S. By the way, at the Virginia Beach meeting I raised a number of
objections to the assumptions put forward for some of the scenarios,
i.e. LEO-ground, but I couldn't find any trace of them 
        in the minutes. 

---------------------------------------------------
Massimo Bertinelli
Communication Systems Engineer
ESA/Estec

Tel. +31 (0)71 5653435
-------------------------------------------------- 

<Nicolas.Perlot at dlr.de> 
Sent by: sls-com-bounces at mailman.ccsds.org 

04/07/2010 13:56 

To

<sls-com at mailman.ccsds.org> 

cc

Subject

[Sls-ocm] Charter draft for OCM working goup

Dear Lasercom people,

Find attached a draft of the charter for the creation of a CCSDS working
group "Optical coding and modulations".
Please send me your feedback within 3 weeks (till July, 26th). If your
agency is a CCSDS member agency, check whether it indeed supports the
specific scenarios as established in the last column of the scenario
table.

Regards,

Nicolas Perlot
Chair of the SIG "OCM"
[attachment "Proposed_Charter_OCM_WG.doc" deleted by Massimo
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