Planning and scheduling of Operations of Small atellites

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Planning and scheduling of Operations of Small
atellites
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• INTRODUCTION
• Small satellites
• ? a great development has been made
• ? operate in near earth orbit
• ? works alone or some of them work together
  as a constellation for a special purpose
• ? lightweight and compact structures
• ? the cost of small satellite is lower than
  that of ordinary satellite
• ? How to efficiently plan and schedule
  operations of Small satellites

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Chinas S-band ground tracking Network China's
S-band space TTC network is mainly comprised of
five TTC stations, a network operation and
management center (NOMC), a number of mission
centers and a data exchange system consisting of
geostationary communication satellites and ground
data switching network.
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The stations are located Kashi (KS, in Xinjiang
autonomous district), Weinan (WN, near Xian in
Shanxi province), Qindao (QD, in shandong
province), Xiamen (XM, in Fujan province) and
Nanning (NN, in Guangxi autonomous district).
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These stations can be divided into two classes.
One class are Weinan TTC Station, Qindao TTC
Station and Xiamen TTC Station which are used
for TTC of medium and low earth orbit
spacecraft. The other are Kashi and Nanning TTC
stations which can used for geostationary
satellites as well as medium and low earth orbit
spacecraft.
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NOMC

WN


QD

KS

XM
NN

,

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The System Structure of S-TTC Station
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Table Main Technical Specifications of the
S-TTC Stations
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Table Main Technical Specifications of the S-TTC
stations(contd)
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Table Main Technical Specifications of the S-TTC
stations(contd)
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FACTORS AFFECT THE OPERATION COSTS ?
Standards. ? Ground automation and staff
rehearsal. ? Impacts of new satellite
launching. ? Build-up way of ground segment.
? Satellite automatism.
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EFFICIENTLY BUILDING-UP OF GROUND CONTROL
NETWORK ? Commercial Off-Shelf (COTS)
production should be employed to maximum. ?
Software radio technology and re-configurable
technology should be used in the building-up of
the ground station. ? Verification equipment
will be reused ? Mission operators should take
part in the development of the specific
facilities including satellite. ? Distributed
network and database other the large-scale
centralized should be utilized.
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AUTOMATIC COORDINATION AND SCHEDULING OF THE
GROUND OPERATION FACILITIES AND RESOURCES
Similar smallsat missions or each satellite of
the constellation should share the ground
facilities and resources for reducing the mission
budget. The automatic scheduling must be
implemented for that the constellation could be
monitored and controlled by the small-scale
ground system. The two scheduling algorithms
presented here are as follows
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MISSION-ORIENTED PLANNING CRITERIA
The goal of this planning algorithm is to support
maximum missions for the ground network in a
designated period. Service Priority Model A
multi-layered model is used and each layer is
assigned with a priority number. The
corresponding priority Pi should be pre-defined
by different satellite experts and project
managers. Service priority is the main criteria
based on which the scheduling process ranks the
similar missions. In anyway, the layer model
could vary with the service tape.
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MISSION-ORIENTED PLANNING CRITERIA
Mission Priority Model A multi-layered
model is also used and each layer is also
assigned with a priority number. The
corresponding priority Mi should also be
pre-defined by different satellite experts and
project managers. Mission priority is the main
criteria based on which the scheduling process
ranks individual mission. The mission priority
step should be bigger than service priority step
and the mission priority will play more important
role in ranking.
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MISSION-ORIENTED PLANNING CRITERIA
Scheduling Algorithm The common
sources such as stations, hardware and software
and communication links etc. are allotted by
NOMC. Mission centers send their ground network
support requests to NOMC before the defined time
every day. The expected service date and time,
mission type, service type, stations and
parameters should be at least included in the
request. It could contain one day or a few days
support request. After that, The NOMC will rank
these requests with respect to service and
mission priorities and the work status of
network. GNMC calculate the total priority by the
following formula
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MISSION-ORIENTED PLANNING CRITERIA
RiS(KPi Mi) for the first time ,
kgt2 RiS(KPi Mi)/(Dn) , the mission Mi has
been met by n times. D is the layer
difference. As the conflict occurs, the mission,
its Ri is biggest, is assigned to use the
stations, computation resource and database etc.
a mission is randomly allotted as more than two
missions have the biggest priority.
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STATION-ORIENTED PLANNING CRITERIA
The goal function of station-oriented
planning algorithm is minimize the work load of
the network for designed multi-missions. The goal
function is defined as Wmin f(wi, mM)
(i1,,n) w-ratio of work time to total plan
time Ground station equipment status space
and vector is defined as
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STATION- ORIENTED PLANNING CRITERIA
Si(TMTBF,TMTTR,TSW,Tp,Ta,O,P) TMTBF
-MTBF of equipment, TMTTR --MTTR of equipment,
TSW- mission switchover time, Tp-pre-heat time,
Ta-permitted equipment continuous work time,
O-power on times, P-the probability of mission
success The work load coefficient L could be
Llt2 or L2. Llt2 means the work load can be
endured by the equipment. L2 means the equipment
fails.
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STATION- ORIENTED PLANNING CRITERIA
When Llt2, the scheduling probability formula
is Pi1-ß/aMi Where a?/? ,ß?/T
, i- mission number
Mi(an/n!)W/(Aan/n!R) W?8s1(sas/?Sm1(nmß)
A?nk0(ak/k!) R?8s1(as/?Sm1(nmß) ?-the
number of missions per time unit, whose priority
number is bigger than the required. ?-mean
mission executing time, T- mean mission allowed
delay time, n-total number of ground station
equipments.
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STATION- ORIENTED PLANNING CRITERIA
When L2, the scheduling probability formula
is Pi1-an/n!/ (?nj0(an/j!) The
following factors not limited should concerned in
the definition of the work load coefficient, such
as staff handover, vocations of operators. The
final plan should make each ground station have
equal work load. The variance of work load could
be calculated and be within the required range.
If the satisfied resulted could be obtained after
calculation, it is necessary to adjust the
destination function. It means the ground network
could support the required missions if there is
still no satisfied result. One solution is to cut
off some mission, the other is to construct more
stations or add more equipments.  
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