Orbit

The Orbit MFD shows your current trajectory, the selected target's trajectory, and a proposed maneuver around Vieneo. Use it to change your orbit, rendezvous with a station or another spacecraft, or pass over a selected surface point. DOR executes the selected valid orbital plan; circularizing is one possible plan.

This guide covers the new full-page instrument introduced by ticket 672. Older clients may still show the small numerical Orbit readout. The new page is installed in the E-10, E-11, P-13, W-6, T-19 and EVA displays. It is not installed in the A-4.

About the illustrations: These are labeled scenario renders from the implemented instrument's layout, orbital planner and guidance code, using synthetic example conditions. They are not screenshots of live flights. Each uses the native 420 × 320 layout enlarged for reading. Example times, fuel and delta-V are not a performance promise for your vehicle.

Current limits: Orbital adjustment, rendezvous and overflight have executable plans. A powered launch profile and an atmospheric return/landing profile are not implemented. The ground and return examples below show these limits explicitly.

Open and operate the page

Select the Orbit page on a supported vehicle's MFD. Choose the station, spacecraft or surface waypoint on your usual target-selection instrument; Orbit reads that selection. You do not enter a second waypoint on this page.

Control	Action
Shift + Up / Down	Select a row in the side controls. The highlighted row's actions appear along the bottom.
Shift + Left / Right	Change the highlighted option or decrease/increase its value.
Shift + C, with the eccentricity row selected	Request a circular orbit (e = 0).
Your configured DOR on/off control	Engage or disengage execution of the selected valid plan.

The controls require cockpit power and do not take these keys while text entry is active. Changing VIEW does not alter the plan or interrupt DOR. Changing a planning value does interrupt execution: review the new solution before engaging DOR again.

Select an objective

MODE	Use
RENDEZVOUS	An orbiting station or free-flying vessel is selected. Reach a future point on its trajectory and match its velocity there.
OVERFLY	A surface waypoint or grounded vessel is selected. Pass above that rotating ground point at the requested altitude and time.
RETURN	A surface target is selected. This currently displays the situation and ENTRY PROFILE REQUIRED; it does not calculate or execute atmospheric entry or landing.
ADJUST ORBIT	Change your own orbit independently of the selected target. Available through MODE even when a target is selected.

With no target, select ADJUST ORBIT or select a navigation target elsewhere. A target attached to another object is not treated as an independent free-flying spacecraft. An atmospheric-flight target may still have a predicted trajectory, but it is marked with an atmospheric warning.

Rendezvous is more than matching orbital size and shape. Two spacecraft can have identical orbital parameters and remain far apart. Rendezvous also solves for position and velocity at the same future time, including the difference between their orbital planes.

Read the picture and numbers

The graphic area stays the same size in every mode. Green is your current trajectory; cyan is the target; amber dashed lines show the proposed transfer. Dim amber shows the destination orbit, and gray dashed lines show a planned coast before departure. AP and PE mark apoapsis and periapsis. Numbered amber markers identify burns; T identifies the target's current position.

VIEW	What it helps you see
ORBIT	Your orbital plane viewed face-on: shape, apsides and transfer path.
PLANE 3D	Plane orientation, with Vieneo's equator and north axis as references. The NODE line indicates the intersection of the current and target orbital planes.
EDGE-ON	Your orbital plane viewed from its edge. Useful for seeing how far the target or transfer leaves that plane; it compresses the shape of your own orbit into a line.
TRACK	Latitude/longitude ground tracks, including Vieneo's rotation. Useful for a surface overflight. This is a schematic grid, not terrain imagery.

Readout	Meaning
AP / PE	Highest / lowest altitude of the orbit above the spherical Vieneo reference surface, in km. A negative PE means the unpowered trajectory intersects that surface.
e	Eccentricity: 0 is circular; larger values produce a more elongated ellipse.
SIZE … km a	Semi-major axis, measured from Vieneo's center. It is not altitude. The reference radius is 2939.6 km.
i / PLANE DIF	Inclination to Vieneo's equator, or the angle between your plane and the target's plane, in degrees.
TP / nu	Orbital period in seconds / true anomaly in degrees, locating you around the current orbit relative to periapsis.
CURRENT > PLAN	Current values followed by the proposed final values. CURRENT > REQUEST is an editable goal for which no valid plan exists yet.
B1 / B2	Burn countdown, planned delta-V in m/s, estimated duration in seconds and fuel in kg.
TOTAL / FUEL	Total planned delta-V and estimated fuel. Duration and fuel assume the available full-thrust performance.
TO GO / USED	During DOR execution: the active guidance correction remaining, in m/s, and fuel consumed since engagement, in kg.

Ground and ascent

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  Scenario 1: on the ground. A station is selected, but there is no solved powered launch profile. Current orbital elements are unavailable.

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  Scenario 2: ascending through 75 km. The green curve is a measured-state ballistic coast. An in-flight vacuum transfer estimate can appear, with an atmospheric warning; this is not a powered ascent profile.

On the ground, or while rising below 100 km, the graphic automatically becomes ASCENT DETAIL / COAST. It shows the local curved surface and altitude scale. The header says ASCENT / INSERTION, while MODE still describes your chosen objective, such as RENDEZVOUS.

ASCENT PROFILE REQUIRED on the ground means DOR cannot launch you using this planner. There is no optimized launch-window display or continuous heading/pitch schedule for takeoff. Fly the ascent using the vehicle's normal controls. Once airborne, any available transfer estimate starts from your measured position and velocity; it does not include aerodynamic lift or drag in the predicted path.

At 100 km while climbing, the graphic returns to the selected orbital view. This does not certify that you are in orbit: a trajectory whose periapsis intersects Vieneo remains ORBIT INSERTION or SUBORBITAL / ENTRY. A descending vehicle below 100 km is not automatically shown as ascending.

There is no hard atmospheric boundary at 75 or 100 km. The planner's warning estimate uses the client's density model and air-relative speed. The 100 km change is a display rule, not a guarantee that atmospheric forces are negligible.

Change or circularize your orbit

Scenario 3: circularize. The selected e row requests zero eccentricity. The nearly circular starting orbit needs only a small correction in this example.

1. Select MODE → ADJUST ORBIT.
2. Choose LOCK NONE, LOCK AP or LOCK PE. Locking an apsis preserves its selected radius while you change eccentricity. It does not mean “wait to burn at that apsis.”
3. Change e. With LOCK NONE, also change SIZE. Shift+C on the e row requests a circle; without an apsis lock it uses the planned first-burn radius when available, otherwise your current radius.
4. Choose the departure rule under START. Compare the green current orbit with the amber requested orbit, AP/PE, burn count, fuel and warnings.
5. Engage DOR when satisfied with a valid plan, or use the plan as a reference for manual flying.

START NOW asks for a solution from your current position; you do not have to wait for apoapsis or periapsis. START AUTO compares a limited set of candidate departure times, including apsides for orbital adjustment, and chooses the lowest delta-V among valid candidates. It is not a search of every possible launch window. START AT TIME exposes an IN countdown that you can adjust.

If the requested orbit does not pass through the departure point, the planner may propose a transfer and a second burn to establish the new shape. A request that intersects the surface is rejected. SIZE changes in 100 km steps; e changes in 0.01 steps.

Rendezvous with a station or spacecraft

Scenario 4: a station in a different plane. PLANE DIF is about 38°. The cyan orbit and amber transfer leave the green orbital plane; the station does not need to be directly overhead.

1. Select the target on the navigation/target instrument, then choose RENDEZVOUS here.
2. Set MEET to the desired future arrival time. Each adjustment changes the requested interval by five minutes and establishes a new countdown.
3. Compare START NOW, AUTO or AT TIME. If no clear transfer is found, change the arrival or departure time.
4. Use PLANE 3D or EDGE-ON to inspect the plane change, and ORBIT to inspect the transfer shape. Review both burns and the fuel estimate.
5. Engage DOR to execute the selected solution. Continue monitoring the target and warnings.

The planned meeting point is approximately 5 km behind the target along its trajectory. It is a rendezvous staging point, not a docking port or a command to fly into the station's center. Stations follow their modeled motion. Another spacecraft is predicted to coast; if it maneuvers, the original prediction is no longer reliable.

After rendezvous, use the normal close-approach and docking procedures. The Orbit page does not obtain docking clearance or perform docking. TVM remains a separate target-relative velocity control.

Follow DOR through the burns

DOR now follows the selected orbital plan. It supplies pitch and heading targets to the existing flight director and commands translation thrust. Roll remains the pilot's preference; there is no separate roll command on Orbit.

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  Scenario 5: departure, 30 seconds after engagement. DOR BURN; TO GO is about 487 m/s. The B1/B2 rows retain the planned burn budgets.

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  Scenario 6: the same transfer coasting. B1 is DONE. DOR COAST applies no thrust and prepares guidance for the next burn; TO GO now refers to that next correction.

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  Scenario 7: arrival correction. DOR ARRIVAL has begun before the planned meeting time. Live TO GO differs from the original B2 estimate as guidance corrects the actual trajectory.

For a delayed departure, DOR WAIT provides pre-alignment guidance without thrust. After the first burn, DOR COAST also suppresses thrust while retaining the next burn's attitude guidance. During active burns, remaining delta-V is recalculated from the actual state; it need not decrease smoothly or equal the original burn budget. Completion requires the controller to settle near its goal, so finite burns can finish later than the initial estimate.

Use DOR off to take over. Manual thrust-increase/decrease key commands also disengage it. Changing planning values, losing/changing a rendezvous target, losing cockpit power, docking/landing, or changing/resetting the vehicle's flight state cancels execution. After a cancellation, inspect the reason and solve again before re-engaging. VIEW changes alone are safe to make during execution.

Pass over a ground point

Scenario 8: overfly. A surface point is selected, with a 900 km pass in 40 minutes and EXIT COAST. The ground track accounts for Vieneo rotating beneath the flight path.

1. Select a surface waypoint, then choose OVERFLY.
2. Set ALT above the spherical reference surface, in 100 km steps, and PASS time, in five-minute steps.
3. Select EXIT COAST to continue on the transfer orbit after the crossing, or EXIT CIRCULARIZE to establish a circular orbit after passing the waypoint.
4. Set START, inspect the ground track and orbit views, and review the burn estimates before using DOR.

Overfly meets a moving ground location at a chosen time; it does not hover above it. A circularization burn belongs after the crossing and can change where the spacecraft travels afterward. The pass altitude is not clearance above local terrain.

Return and atmospheric entry

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  Scenario 9: return target selected in orbit. RETURN shows the surface target and current orbit, but ENTRY PROFILE REQUIRED means no executable entry solution exists.

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  Scenario 10: descending through 75 km. SUBORBITAL / ENTRY correctly describes a surface-intersecting trajectory. This is a situation display, not an automatic landing profile.

Select the intended surface waypoint and choose RETURN to see the destination in context. Do not expect DOR to deorbit, manage atmospheric entry or land from this mode. No burn duration or fuel solution is supplied until an entry profile exists. Use the vehicle's separate return and landing procedures.

ADJUST ORBIT is not a substitute for an entry planner: a requested final orbit that intersects the spherical surface is rejected. The displayed coast also omits atmospheric drag, terrain and heating, so it cannot establish a landing footprint or a safe entry corridor.

Warnings and unavailable plans

Message	Meaning / next action
VACUUM ESTIMATE	An orbital estimate is available. It assumes two-body coasting between instantaneous planned burns.
LONG BURN - ESTIMATE / FINITE BURN NOT CORRECTED	The preview's instantaneous-burn approximation is weak for the estimated duration. Live DOR corrects from actual state, but the original time, path and fuel are estimates.
ATMOSPHERIC PASS / ATMOSPHERIC TARGET	Atmospheric effects may invalidate the coast prediction. A target in atmospheric flight is also flagged. Review the trajectory and use appropriate flight control; a warning is not proof of a safe route.
SURFACE INTERSECTION / NO CLEAR TRANSFER	The requested shape intersects Vieneo, or no acceptable transfer was found. Raise the requested periapsis or change the timing/objective.
INSUFFICIENT FUEL / PERFORMANCE UNAVAILABLE	Fuel or propulsion data do not support execution. A geometric estimate alone is not an executable DOR plan.
BURN TIME PASSED / ARRIVAL TIME PASSED	The selected deadline has passed. Edit the time to request a new one; these are real countdowns, not indefinitely rolling delays.
SELECT NAV TARGET / NO TARGET TRAJECTORY	Select a usable target, or choose ADJUST ORBIT.
UNDOCK TO PLAN / POWER OFF	Restore the required flight or cockpit-power state before planning/execution.
ASCENT PROFILE REQUIRED / ENTRY PROFILE REQUIRED	Powered launch / atmospheric return guidance is unavailable in this version.