Station Keeping
Services provide an
integrated graphical environment for planning and reconstructing station keeping maneuvers
for spacecraft relative to a nominal on-station orbit. The service
supports Frozen Orbit Station Keeping,
Geostationary
Equatorial Station Keeping,
Sun Synchronous Repeating Ground Track
Station Keeping, and Vader Orbit Station Keeping. The Service supports
planning and reconstruction of drift phasing maneuvers, eccentricity vector maneuvers, coordinated two-part
drift and eccentricity vector maneuvers, and inclination vector maneuvers. Graphical
Maneuver Editors or an
alternative text based Maneuver Services
editor are available.
The Graphical Maneuver Editors map the ephemeris and any maneuvers
posted against it into one of three station keeping maneuver phase spaces:
drift, eccentricity, and inclination. The station keeping phase spaces characterize the
departures of the actual orbit from
the nominal orbit specification in the database (spacecraft->nominal_orbit).
The Maneuver Services text dialog supports
direct modification of the post-maneuver elements or the maneuver deltas. Orbit Determination Services
support maneuver evaluation through estimation of thrust correction factors.
Maneuvers are planned with respect to the reference ephemeris buffer
(see Ephemeris Services)
based on mean elements derived from harmonic analysis of the reference ephemeris using
first and second harmonics of the orbital period, the lunar period, and the solar period.
By creating a thrust profile based on the maneuver plan, analysts may validate the plan by
propagating a high fidelity ephemeris through the burn (Ephemeris Services).
Maneuvers [single-selection list]
Select the maneuver for subsequent View, Edit or Delete
as the Current Maneuver.
Next Maneuver
[radio buttons]
Inclination [radio button]
Drift & Eccentricity
[radio button]
Two Part D&E [radio button]
Two Part I&E [radio button]
The radio button controls which type of maneuver is to be
inserted in response to the Insert pushbutton
action. Note that Insert Maneuver mouse actions within one of the
graphical maneuver contexts override the radio button setting. For
example, inserting a maneuver in the Inclination
Planner will insert an inclination maneuver and reset the radio button to
reflect the insertion.
Attitude [option menu]
Maneuver services can hold the attitude constant (Freeze)
or can calculate (Adjust) the optimal attitude for the maneuver(s).
Current Maneuver
[view/edit fields]
Summarizes the attributes of the selected maneuver.
Maneuver ID [edit field]
Maneuver sequence prefix.
Maneuver Type [display field]
View field based on maneuver type.
Command Antenna [display field]
View
text field to identify the ground station antenna which will uplink
the maneuver message. The range to this antenna influences the jet
start angle phase delays for pulsed mode thrusters on spinning vehicles.
Thruster Configuration [display field]
View field of the thruster configuration to be used to supply the delta V.
Thrust Profile Type [option menu]
Select the type of thrust profile to be written in response to the Create
Thrust Profile pushbutton action.
Continuous Thrust
profile comprises a time history of spacecraft body frame thrust, mass flow
rate, and the attitude of the spacecraft. The ephemeris propagator integrates
the rates through burn.
Impulsive Thrust profile
comprises spacecraft body frame delta
V, delta M, and spacecraft attitude at one or more discrete burn centroid
times. The ephemeris propagator applies each velocity and mass
discontinuity [impulse] at the burn centroid time.
Epoch [time edit field]
Burn centroid time.
Burn Duration [numeric edit field]
Required burn duration to achieve the requested delta-V
Delta V [numeric edit field]
Delta-V vector.
Delta M [numeric display field]
Mass requried.
Insert [pushbutton]
Insert a new maneuver.
Insert All [pushbutton]
Insert all the maneuvers in the interval of the
Maneuver Window.
Apply [pushbutton]
Apply any pending edits to the current maneuver.
Cancel [pushbutton]
Cancel any pending edits to the current maneuver.
Delete [pushbutton]
Delete the current maneuver.
Delete All [pushbutton]
Delete all the maneuvers.
Maneuver States [pushbutton]
Display Pre-Maneuver, Differential, and Post-Maneuver
states for the current maneuver. You can select the frame in which to display the orbital
elements. Selected components of the differential and post-maneuver states are edit-enable
in the Station Keeping frames. You can specify target drift or delta inclination,
for example, and the Burn Duration, Delta V, and Delta M
will be re-computed.
Orbital Elements [option menu]
Total Mass [pushbutton]
Activates the Mass
of Maneuver States dialog.
Mass of Maneuver States
[dialog]
The Mass of Maneuver States dialog shows the Pre-Maneuver,
Delta, and Post-Maneuver values of the fuel mass, for each of the fuel
sub-systems (Fuel Sys A, Fuel Sys B,...).
Constraints
[dialog]
Used to define maneuver time constraints and post maneuver
orbit constraints. OASYS uses the events search engine to evaluate
maneuver constraints.
Available Constraints
[list]
List to f all the maneuver constraints defined in the
database.
Selected Constraints
[list]
List o f all the constraints to search for.
Add [pushbutton]
Delete [pushbutton]
Move [pushbutton]
Move constraints from the available list to the selected
list for constraint checking.
Edit Constraints
[pushbutton]
Activates the
Maneuver Constraint
Editor dialog.
Status [text view field]
Displays the results of the constraints check.
Check Burn 1
Constraints [pushbutton]
Check Burn 2 Constraints
[pushbutton]
Check the constraints against the specified burn.
Clear Constraint
Messages [pushbutton]
Clears the current constraint messages
from the status window.
Adjust
Maneuver To Avoid Constraints [pushbutton]
If a constraint violation occurs move the burn outside the
constraint region, if possible - this can only be applied to maneuver time
constraints.
Maneuver Setup
[pushbutton]
Activates the Station Keeping Maneuver Setup dialog.
Create Thrust Profile [pushbutton]
Creates or appends thrust records for the Current Maneuver
to the Thrust
Profile buffer.
Save SK Ephemeris
Save the Station Keeping ephemeris to disk. This
ephemeris contains all the inserted maneuvers.
Drift Planner [pushbutton]
Activates the Drift Maneuver
Planner dialog.
Eccentricity Planner
[pushbutton]
Activates the
Eccentricity
Maneuver Planner dialog.
Inclination Planner
[pushbutton]
Activates the
Inclination
Maneuver Planner dialog.
Station
Keeping Maneuver Setup [dialog]
The Station Keeping Maneuver Setup dialog is an instance of the
Notebook widget.
Thruster Configuration
[pane]
Inclination Mnvr
Drift & Ecc Mnvr
Two Part D&E [Mnvr 1]
Two Part D&E [Mnvr 2]
Two Part I&E [Mnvr 1]
Two Part I&E [Mnvr 2]
[pushbuttons]
Select the Thruster Configuration to be used for a maneuver of the each
type.
Command Antenna [text field]
Select the identifier for the ground station antenna which
will uplink the maneuver message or maneuver commands to the
spacecraft. The spacecraft range from this antenna influences the
jet start angle phase delays for pulsed mode thrusters on spinning
vehicles.
Auto Target Configuration
[pane]
Specifies the nature of the target graphic and the automatic targeting
strategy to be used for maneuvers of each type.
Inclination [option menu]
Maximum Compensation [menu
item]
Specifies that the inclination maneuver target graphic represent the
maximum
compensation inclination strategy, which maximizes cycle duration
by targeting the inclination vector to pass through the origin at the
cycle midpoint.
Track Back Chord [menu item]
Specifies that the inclination maneuver target graphic represent the
track
back chord inclination maneuver strategy—the chord of the inclination departure
from nominal over the cycle is centered on the origin.
Minimum Fuel [menu item]
Specifies that the inclination maneuver target graphic represent the
minimum fuel inclination strategy—the position of the target graphic reflects only
the secular trend in inclination, so that the maneuver does not counteract the cyclic
transverse effects. This target strategy is available only for
geostationary equatorial station
keeping.
Minimum Fuel Init
[menu item]
Specifies the that the inclination target graphic represents the initialization
necessary to adhere to the Minimum Fuel strategy in subsequent
maneuvers. This target strategy is available only for
geostationary equatorial station
keeping.
Drift [option menu]
Operational
Cycle [menu
item]
Maximal Mean Cycle [menu
item]
Maximal Osculating Cycle [menu
item]
The drift target graphic reflects a drift cycle of the
selected duration.
Eccentricity [option menu]
Constant Offset [menu
item]
The eccentricity target graphic reflects a constant
offset from the nominal orbit eccentricity vector. Used to
implement geosynchronous collocation strategies.
SunSynch Offset [menu
item]
The eccentricity target graphic reflects a constant
offset relative to the right ascension of the sun. Available only for
geosynchronous nominal orbits, this offset strategy is used to
implement solar sailing eccentricity vector control strategies.
Two Part D&E [option menu]
Both Drift & Ecc [menu
item]
Drift w/ Ecc Fixed [menu
item]
Ecc w/ Drift Fixed [menu
item]
Two part drift and eccentricity maneuvers adjust
themselves according to the selected strategy.
Two Part I&E [option menu]
Both Inc & Ecc [menu
item]
Inc w/ Ecc Fixed [menu
item]
Ecc w/ Inc Fixed [menu
item]
Two part inclination and eccentricity maneuvers adjust
themselves according to the selected strategy.
Maneuver Cycles [pane]
Osculating Drift Cycle
[numeric display field]
The length of the longest drift cycle which keeps the
osculating phase error within the phase constraint tolerance. The
osculating phase error includes eccentricity and inclination effects.
This is a derived [computed] parameter.
Mean Drift Cycle [numeric
display field]
The length of the longest drift cycle which keeps the
mean phase error within the phase constraint tolerance. The mean
phase error ignores eccentricity and inclination effects. The Mean Drift
Cycle is the green trace displayed on the SK Drift Planner. This is a
derived [computed] parameter.
Drift Tolerance
[numeric display field]
The phase tolerance [phase box half-width] which
corresponds to the Mean Drift Cycle. The drift cycle tolerance is a
spacecraft database parameter. See spacecraft->nominal_orbit.
Operational Drift Cycle
[numeric edit field]
The length of the operational drift cycle desired by
the operator. Constrained to be shorter than the Mean Drift
Cycle, the Operational Drift Cycle is typically set to regularize ground
station operations with respect to drift maneuvers. The Operational
Drift Cycle is the yellow target trace displayed on the SK Drift
Planner. Changes in the Operational Drift Cycle are reflected as
changes in the Operational Drift Tolerance below. The Operational Drift
Cycle is a user interface database parameter. See
ui->skm_ui.ew_cycle.
Operational Drift Tolerance
[numeric edit field]
The phase tolerance [phase box half-width] which
corresponds to the Operational Drift Cycle. Changes in the Operational
Drift Tolerance are reflected as changes in the
Operational Drift Cycle above.
Inclination Cycle [numeric
display field]
The length of the longest inclination cycle which
keeps the inclination vector error within the inclination error
constraint tolerance.
Inclination Tolerance
[numeric
display field]
The inclination error constraint tolerance which
corresponds to the length of the Inclination Cycle above.
The inclination tolerance is a spacecraft database parameter. See
spacecraft->nominal_orbit
Operational Inclination
Cycle [numeric edit field]
The length of the operational inclination cycle
desired by the operator. Constrained to be shorter than the
[maximal] Inclination Cycle, the Operational Inclination cycle is
chosen to regularize ground station operations with respect to
inclination maneuvers. Changes to the Operational Inclination Cycle are
reflected as changes in the Operational Inclination Tolerance
below. The Operational Inclination Cycle is a user interface database
parameter. See ui->skm_ui.ns_cycle.
Operational
Inclination Tolerance [numeric edit field]
The inclination error constraint tolerance which
corresponds to the length of the Operational Inclination Cycle above.
Changes to the Operational Inclination Tolerance are reflected as
changes in the Operational Inclination Cycle above.
Maneuver Window [pane]
Maneuver Window
[dataspan]
Defines the active window for maneuvers.
Inclination Maneuver Planner
[graphical maneuver editor]
The Inclination Maneuver Planner is a graphical maneuver editor
for inclination maneuvers. Based on a rectangular plot of the inclination vector
error components,
dp = p-P, dq = q-Q,
where
p = 2tan(i/2)cosW ,
q = 2tan(i/2)sinW ,
are the inclination components for the actual orbit and P,
Q are defined analogously for the nominal orbit, the
Inclination Planner allows the user to edit
inclination burns using a point and click mouse interface.
Inclination
Maneuver Planner Legend [dialog]
Traces:
The Inclination Planner trace colors below are the defaults for
OASYS
as shipped. The plot Legend dialog displays the trace definitions and colors for
OASYS
as configured by the user.
Blue Pre-maneuver reference ephemeris.
Cyan Post-maneuver planned ephemeris.
Yellow Maneuver target locus. Reacts to the setting of the
Inclination
Target pushbutton and the Inclination Maneuver
Cycle length.
Red Active maneuver delta inclination.
Red Locus of inclination vectors achievable with a burn of the
current magnitude.
Green Maximum inclination departure from nominal.
Mouse Functions:
Insert Mnvr Insert an inclination
maneuver at node of Reference Ephemeris closest to mouse cursor.
Resize Mnvr Edit the current
inclination maneuver. The inclination (vector) delta is represented by the red trace. You
can change the epoch of the inclination burn without changing its magnitude by pointing to
any point on the red reference burn locus.
Drift Maneuver Planner
[graphical maneuver editor]
The Drift Maneuver Planner is a graphical maneuver editor for
drift (along-track phase) maneuvers. The Drift Planner displays a rectangular plot
of along-track phase drift versus phase error. Phase error is the
departure of actual in-orbit angle from nominal in-orbit angle. Phase
drift is the rate of change of mean phase error. The Drift
Planner allows the user to edit drift burns using a point and click mouse interface.
The effects on eccentricity are automatically computed and are available for display or
modification in the Eccentricity Planner.
Drift Maneuver Planner
Legend [dialog]
Traces:
Maneuver trace colors below are the defaults for OASYS as shipped. The
plot Legend dialog displays the trace definitions and colors for OASYS as
configured.
Blue Pre-maneuver reference ephemeris.
Cyan Post-maneuver planned ephemeris.
Yellow Maneuver target locus. Reacts to the
Along Track Drift Cycle.
Green Maximal drift cycle.
Red Active maneuver delta drift.
Mouse Functions:
Insert Mnvr Insert a drift maneuver at node of Planned
Ephemeris closest to mouse cursor.
Resize Mnvr Edit the current drift maneuver. The red trace
represents delta drift due to the maneuver. Check the effect of the maneuver on eccentricity by invoking the
Eccentricity
Planner from the main Station Keeping dialog.
Eccentricity Maneuver Planner
[graphical maneuver editor]
The Eccentricity Maneuver Planner is a graphical maneuver editor
for eccentricity maneuvers. Based on a rectangular plot of the eccentricity vector
error components,
dh = h-H, dk = k-K,
where
h = e cos(w +
W ), k = e
sin(w +
W ),
are the eccentricity vector components for the actual orbit,
and H,K are the analogously defined eccentricity vector components for the
nominal orbit, the Eccentricity Planner allows the user to edit eccentricity
burns using a point and click mouse interface. The effects on drift are automatically
computed and are available for display or modification in the
Drift Planner.
Eccentricity Maneuver Planner
Legend [dialog]
Traces:
Maneuver trace colors below are the defaults for OASYS as shipped. The
plot Legend Dialog displays the trace definitions and colors for OASYS as
configured.
Blue Reference ephemeris.
Cyan Planned ephemeris.
Green Locus of maximum allowable eccentricity
departure from nominal.
Red Locus of eccentricity vectors achievable with a burn of the
current magnitude.
Red Active maneuver delta eccentricity.
Mouse Functions:
Insert Mnvr Insert an eccentricity maneuver at node of
Planned
Ephemeris closest to mouse cursor.
Resize Mnvr Resize the current eccentricity maneuver. The
eccentricity vector delta is represented by the red trace. You can change the epoch of the eccentricity burn without
changing its magnitude by pointing to any point on the green reference burn locus.
