A Semi-Analytical Method for Calculating Revisit Time for Satellite Constellations with Discontinuous Coverage Nicholas H. Crisp a,* , Sabrina Livadiotti a , Peter C.E. Roberts a a School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, George Begg Building, Sackville St, Manchester, M13 9PL Abstract This paper presents a unique approach to the problem of calculating revisit time metrics for different satellite orbits, sensor geometries, and constellation configurations with application to early lifecycle design and optimisation processes for Earth observation missions. The developed semi-analytical approach uses an elliptical projected footprint geometry to provide an accuracy similar to that of industry standard numerical orbit simulation software but with an efficiency of published analytical methods. Using the developed method, extensive plots of maximum revisit time are presented for varying altitude, inclination, target latitudes, sensor capabilities, and constellation configuration, providing valuable reference for Earth observation system design. Keywords: Revisit time; satellite constellation; discontinuous satellite coverage; Earth observation. 1. Introduction During the design of Low Earth Orbit (LEO) systems of satellites performance metrics are required to evaluate different orbital configurations and payload specifications. For Earth observation or communications missions the ex- tent of coverage of the system or rate at which the system visits or views different locations is of particular interest to the mission designer. Revisit time (also known as the response time or coverage gap) is often used as a key per- formance metric for LEO systems which do not have con- tinuous coverage of an area of interest and is defined as the duration in time between consecutive viewings of a given location on the Earth. Most commonly, the Maximum Re- visit Time (MRT) and Average Revisit Time (ART) over a given target area and period of analysis are considered during the mission design process. With increasing on-orbit capability and reduced sys- tem cost, development of constellations of small satellites has recently grown significantly. However, the design and optimisation of these systems is complex and multidisci- plinary, owing to the number of different design variables and ranges which they can take. For example, consider- ation of the orbit design, system configuration, payload characteristics, and mission performance can all have a * Corresponding author. Email addresses: [email protected] (Nicholas H. Crisp), [email protected] (Sabrina Livadiotti), [email protected] (Peter C.E. Roberts) significant effect on the final system utility and cost. For an Earth observation satellite or constellation the evalua- tion of revisit time therefore forms a critical component of the design and optimisation process. Often the analysis of coverage or revisit metrics for satellites and constellations is performed using commer- cially available orbital propagation and simulation soft- ware such as STK (Systems Tool Kit) [1, 2, 3]. However, due to the numerical nature of these programs and po- tential for long analysis periods (on the order of minutes) or large numbers of satellites, the computational time can become considerable. Furthermore, when many cases are to be considered, for example within a wider framework for system optimisation, a faster, open, and stand-alone method is preferred. A number of methods for calculating revisit time have been discussed and applied in the literature. Wertz [4, 5] provides basic descriptions for evaluating coverage using simple analytical expressions and calculating revisit met- rics using two numerical treatments. The first, a numerical method, utilises simple ground track plots and mission ge- ometry and is shown to be most useful for rapid mission analysis. The second, point coverage simulation methods, use a grid of points at which visibility characteristics are be evaluated. These methods are able to provide insight into the statistical measures of coverage and can achieve greater accuracy albeit at the cost of longer computation times. Bottkol and DiDomenico [6] describe a numerical phase- based approach to the calculation of revisit interval. In this method the satellite ground track is mapped to the surface of a torus which is then unwrapped to indicate the intersection with a defined visibility region. The devel- Preprint submitted to arXiV cs.CE July 6, 2018 arXiv:1807.02021v1 [cs.CE] 5 Jul 2018
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Accelerating FDIs in the manufacturing sector:Perspective from Japanese manufacturers
Mar 2012
Nomura Research Institute (NRI)
DTI/BOI “Trade and Industry Talks”
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 1
1. Changes in Japanese manufacturers’ momentum
2. Market and supplier for Japanese manufacturers
3. Ways forward for the Philippines
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 2
East Japan Earthquake/Tsunami in Mar 2011 triggers
1. Suspension in domestic supply chain Due to infrastructure damages
2. Rotational power shortage to continue in coming years Due to nuclear radiations defect
3. Reminder of aging society and declining labor forces
2Picture: Ministry of Foreign Affairs
President’s Visit to Tsunami-hit Area, Sep 2011
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 3
Hyper appreciation of Japanese Yen
1. Depriving the domestic manufactures with competitiveness2. Making manufacturing in Japan more difficult
3
JPY/USD (Yearly Average)
110.21116.38 117.84
103.46
93.5787.81
79.84
60
70
80
90
100
110
120
2005 2006 2007 2008 2009 2010 2011
JP
Y/U
SD
Data: Bank of Tokyo-Mitsubishi UFJ, Ltd.
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 4
Capability of Employees
37.9
40.9
42.2
45.8
47.6
48.7
0 10 20 30 40 50 60
Philippines
Thailand
Indonesia
India
China
Vietnam
%
Labor issues in China and Vietnam
1. Labor disputes and strikes2. Inflating labor costs3. Difficulty in hiring managers/workers at reasonable costs
4Data: JETRO, “Survey of Japanese-Affiliated Firms in Asia and Oceania,” Oct 2011
Problems Faced by Japanese Companies in AsiaInflat ing Labor Costs
48.4
68.3
75.2
80.3
83.3
84.9
0 20 40 60 80 100
Philippines
Thailand
Indonesia
India
Vietnam
China
%
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 5
Aging Asian countries but the Phils.
Working age (15-64) population shall start declining during 2010s in China, during 2020s in Thailand, and during 2030s in Indonesia and Vietnam.
5Data: UN, “World Population Prospects: The 2010 Revision”
Working Age (15-64) Population
Philippines
Vietnam
Indonesia
Thailand
China0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060
Y2010=1
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 6
FDI to the Phils. (approval basis)
17.131.9
62.355.4
0
20
40
60
80
100
2010 2011
(Q1 to Q3)
Php b
il.
Others
Japanese
Emerging interests to the Phils.
Now, the choice in ASEAN is either Indonesia or the Phils. The Phils. is vested with availability in developed landsite,
abundant labor forces, efficient PEZA and legalized investment incentives.
6Data: NSCB, “FDI Quarterly Report,” Q3 2011
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 7
Big names and big tickets to the Phils.
Those final assembly manufacturers will need suppliers soon. Supporting industries are in necessity.
7
Batangas$220MPrinterCanon
Clark$625MTireYokohama
Batangas$ 40MCeramic condenser
MurataLagunaHealthcareLion
$110M
$ 54MAmount
Printer
PrinterProductionCompany Site
Newcomer Brother Batangas
Expansion Epson Batangas
Select Japanese Investments committed since 2011
Source: Compiled by NRI
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 8
1. Changes in Japanese manufacturers’ momentum
2. Market and supplier for Japanese manufacturers
3. Ways forward for the Philippines
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 9
Local Procurement Ratio
26.3
28.7
39.3
41
41.1
53
59.7
0 10 20 30 40 50 60
Philippines
Vietnam
Malaysia
Indonesia
India
Thailand
China
%
Share of Export in Sales
15.3
30.1
30.4
34.7
45
54.4
57.7
0 10 20 30 40 50 60
India
Thailand
Indonesia
China
Malaysia
Philippines
Vietnam
%
Japanese manufacturing patterns in the Phils.
1. Market: export oriented, rather than domestic.2. Supply: nearly half from Japan, rather than onshore
sourcing.
9Data: JETRO, “Survey of Japanese-Affiliated Firms in Asia and Oceania,” Oct 2011
Market and Supplier for Japanese Companies in Asia
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 10
Position of countries from Japanese manufacturers’point of view
10
Onshore sourcing
Offshore sourcing
Domestic market
Export oriented
China
Thailand
Indonesia
VietnamPhilippines
MalaysiaIndia
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 11
Case in point: Flooding in Thailand
More than 400 Japanese manufacturers/factories shut down Some reassigning production capacities more to the Phils. NIDEC, Rohm Electronics, Toshiba, etc.
11
Company Loss Company LossToyota Motors 1,500 Hitachi 375Honda 1,375 NIDEC 375Sony 875 Nikon 313Panasonic 750 Rohm 238Toshiba 500 Fujitsu 213
(Unit: US$M)Estimated Net Profit Loss due to Thai Flooding
Note) for fiscal year ending Mar 2012Data) Nikkei news article on Feb 7, 2012
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 12
Case in point (cont.): Thailand after flooding
However, only a few have decided to close Thai factories Sanyo Semiconductor and Sumiko Leadframe
Almost all Japanese manufacturers have decided to remain within Thailand. Why?
1. Domestic sales: Their main market is in Thailand. Regardless of nationality of client.
2. Onshore sourcing: More than half of their supplies come from Thailand. Regardless of nationality of supplier.
12
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 13
Lessons to the Phils.
1. Development of domestic sales base1. By domestic consumption? => Not now, presumably.2. By promotion of final assembly? => Yes
2. Development of onshore supporting industry.1. By local contents requirement/regulation?
for other purpose than the rule of origin under AFTA-CEPT?2. By market force?
with public sector support or facilitation?
13
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 14
1. Changes in Japanese manufacturers’ momentum
2. Market and supplier for Japanese manufacturers
3. Ways forward for the Philippines
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 15
Promotion of final assembly
1. Electronics products (non-semiconductor) Target product: printer, multifunctional peripheral (MFP), projector,
scanner, digital camera, etc.▪ Electronics products which have commonality with existing products▪ Products whose increasing demand is in emerging markets
Target Japanese companies
15
Canon, EpsonPFUScanner
Canon, PanasonicCasio, Fuji Film, Nikon, Sony
Digital camera
Canon, Hitachi, PanasonicProjector
ToshibaToshiba TEC, RicohPrinter/MFP
Manufacturing in the Phils., but no product line of it
Not manufacturing in the Phils.
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 16
Promotion of final assembly (cont.)
2. Shipbuilding Target Japanese companies: Member of Shipbuilders’ Association of
Japan▪ 19 member companies are still shipbuilding in Japan at most, except for
Tsuneishi (in China and the Phils.) and Kawasaki (in China).
Shipbuilding may trigger investment by steelmakers16
DockyardAffiliate
In the Phils.
Branch
Affiliate
Affiliate
In the Phils.Onomichi DockyardHakodate Dock
Sumitomo Heavy Industries
Universal ShipbuildingTsuneishi ShipbuildingMitsui Engineering & Shipbuilding
Namura ShipbuildingNaikai Zosen
Mitsubishi Heavy IndustriesShin Kurushima Toyohashi ShipbuildingKoyo DockyardShin Kurushima DockyardKawasaki Heavy IndustriesSasebo Heavy IndustriesImabari Shipbuilding
Oshima Shipbuilding
Sanoyas ShipbuildingIHI Marine United Inc.
IHI Corporation
Member companyMember company
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 17
Promotion of onshore supporting industry
1. Suppliers for electronics products (non-semiconductor) Target product: glass, motor, metal processing, die and mold, etc.
▪ Products which manufacturers of final assembly import at current Target Japanese companies: Mabuchi Motor, Minebea, etc.
2. Onshore sourcing exhibition and booklet Business matching between final assembly and suppliers in the Phils.
▪ Organizer: PEZA in cooperation with BOI/CDC/SBMA▪ Benchmark: Thai BOI Fair
3. Tax Credit Certificate (TCC) matters▪ TCC financially discourages non-PEZA registered companies to supply to
PEZA registered companies, and hence needs to be replaced with cash refund, in line with President's 2012 Budget Speech
17
Copyright（C） 2012 Nomura Research Institute, Ltd. All rights reserved. 18
Contacts
DisclaimerThe information expressed in this material does not necessarily reflect the views or policies of Japan International Cooperation Agency (JICA) or its consultant, Nomura Research Institute (NRI). The information herein is believed to be reliable at the date of its preparation and is provided for information and discussion purposes only. JICA or NRI does not guarantee the accuracy of the information included in this material and accepts no responsibility for any consequence of their use.
Nomura Research Institute Kengo Mizuno, Manila Branch
Tel [email protected]://www.nri.co.jp/english/
18
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