CubeSat Vehicle Earth (Nadir) Pointing

Model CubeSat vehicle whose primary alignment vector points towards center of Earth

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Libraries:
Aerospace Blockset / Spacecraft / CubeSat Vehicles

Alternative Configurations of CubeSat Vehicle Earth (Nadir) Pointing Block:
Cubesat Vehicle Sun Tracking | Cubesat Vehicle Custom Pointing

Description

The CubeSat Vehicle blocks model CubeSat vehicles to provide a high level mission planning/rapid prototyping option to quickly model and propagate satellite orbits, one satellite at a time. (To propagate multiple satellites simultaneously, see the Orbit Propagator block.) To accommodate constellation planning workflows, you can also use these blocks multiple times in a model. Specify this information for the vehicle:

• Initial orbital state

• Attitude control (pointing) mode

The library contains three versions of the CubeSat Vehicle block preconfigured for these common attitude control modes. To select these configurations, set the Pointing mode parameter.

• CubeSat Vehicle Earth (Nadir) Pointing — Primary alignment vector points towards the center of the Earth

• CubeSat Vehicle Sun Tracking — Primary alignment vector points toward the Sun

• CubeSat Vehicle Custom Pointing — Custom alignment and constraint vectors

Ports

Input

A_ECEF (m/s²) — Vehicle accelerations

vector of size 3

Vehicle gravity accelerations (including gravity) used for orbit propagation, specified as a vector of size 3, in m/s².

Data Types: single | double

1st Alignment_Body — Primary alignment vector

three-element vector

Primary alignment vector, in the Body frame, to align with primary constraint vector.

Data Types: double

1st Constraint_ECI — Primary constraint vector

three-element vector

Primary constraint vector specifying the direction in which to align the primary alignment vector.

Dependencies

This port is not available when Pointing mode is set to Earth (Nadir) Pointing or Sun Tracking, which have implied primary constraint vectors.

Data Types: double

1st Alignment_Body — Primary alignment vector

three-element vector

Primary alignment vector, in the Body frame, to align with primary constraint vector.

Data Types: double

1st Constraint_ECI — Primary constraint vector

three-element vector

Primary constraint vector specifying the direction in which to align the primary alignment vector.

Dependencies

• The direction depends on the Constraint coordinate system.

• This port is not available when Pointing mode is set to Earth (Nadir) Pointing or Sun Tracking, which have implied primary constraint vectors.

Data Types: double

2nd Alignment_Body — Secondary alignment vector

three-element vector

Secondary alignment vector, in the Body frame, to align with secondary constraint vector.

Data Types: double

2nd Constraint_ECI — Secondary constraint vector

three-element vector

Secondary constraint vector specifying the direction in which to align the secondary alignment vector.

Dependencies

The direction depends on the Constraint coordinate system.

Data Types: double

Output

X_ECEF — CubeSat position

three-element vector

Earth-centered Earth-fixed CubeSat position components, specified as a 3-by-1 array.

Data Types: double

V_ECEF — Velocity components

3-by-1 array

Earth-centered Earth-fixed velocity components, specified as a 3-by-1 array.

Data Types: double

q_ECI2Body — Quaternion rotation

4-by-1 array

Quaternion rotation from Earth-centered inertial frame to Body frame.

Data Types: double

q_ECEF2Body — Quaternion array

4-by-1 array

Quaternion rotation from Earth-centered Earth-fixed frame to Body frame.

Data Types: double

Parameters

Start date [Julian date] — Initial start date of simulation

2458488 (default) | Julian date

Initial start date of simulation. The block defines initial conditions using this date.

Tip

To calculate the Julian date, use the juliandate function.

Programmatic Use

Block Parameter: sim_t0

Type: character vector

Values: Julian date

Default: '2458488'

CubeSat Orbit

Input method — Initial vehicle

Keplerian Orbital Elements (default) | ECI Position and Velocity | ECEF Position and Velocity | Geodetic LatLonAlt and Velocity in NED

Initial vehicle position and velocity input method.

Dependencies

Selecting the Keplerian Orbital Elements input method enables these parameters:

• Epoch of ECI frame [Julian date]

• Semi-major axis [m]

• Eccentricity

• Inclination [deg]

• Right ascension of the ascending node [deg]

• Argument of periapsis [deg]

• True anomaly [deg]

• True longitude [deg] (circular equatorial)

• Argument of latitude [deg] (circular inclined)

• Longitude of periapsis [deg] (elliptical equatorial)

Selecting the ECI Position and Velocity input method enables these parameters:

• Epoch of ECI frame [Julian date]

• ECI position vector [m]

• ECI velocity vector [m/s]

Selecting the ECEF Position and Velocity input method enables these parameters:

• ECEF position vector [m]

• ECEF velocity vector [m/s]

Selecting the Geodetic LatLonAlt and Velocity in NED input method enables these parameters:

• Geodetic latitude, longitude, altitude [deg, deg, m]

• NED velocity vector [m/s]

Programmatic Use

Block Parameter: method

Type: character vector

Values: 'Keplerian Orbital Elements' | 'ECI Position and Velocit' | 'ECEF Position and Velocity' | 'Geodetic LatLonAlt and Velocity in NED'

Default: 'Keplerian Orbital Elements'

Epoch of ECI frame [Julian date] — Epoch of ECI frame

2451545 (default) | Julian date

Epoch of ECI frame, specified as a Julian date.

Tip

To calculate the Julian date for a particular date, use the juliandate function.

Programmatic Use

Block Parameter: epoch

Type: character vector

Values: Julian date format

Default: '2451545'

Semi-major axis [m] — CubeSat semi-major axis

6878137 (default) | axis in meters

CubeSat semi-major axis (half of the longest orbit diameter), specified in m.

Programmatic Use

Block Parameter: a

Type: character vector

Values: scalar

Default: '6878137'

Eccentricity — Orbital eccentricity

0 (default) | eccentricity greater than or equal to 0

Deviation of the CubeSat orbit from a perfect circle.

Programmatic Use

Block Parameter: ecc

Type: character vector

Values: scalar

Default: '0'

Inclination [deg] — Tilt angle of CubeSat orbital plane

0 | degrees between 0 and 180

Tilt angle of CubeSat orbital plane, specified between 0 and 180 deg.

Programmatic Use

Block Parameter: incl

Type: character vector

Values: scalar

Default: '0'

Right ascension of the ascending node [deg] — Angular distance in equatorial plane

0 (default) | degrees between 0 and 360

Angular distance in equatorial plane from x-axis to location of the ascending node (point at which the satellite crosses the equator from south to north), specified between 0 and 360 deg.

Programmatic Use

Block Parameter: omega

Type: character vector

Values: scalar

Default: '0'

Argument of periapsis [deg] — Angle from CubeSat body ascending node to periapsis

0 (default) | degrees between 0 and 360

Angle from the CubeSat body ascending node to the periapsis (closest point of orbit to Earth), specified between 0 and 360 deg.

Programmatic Use

Block Parameter: argp

Type: character vector

Values: scalar

Default: '0'

True anomaly [deg] — Angle between periapsis and current position of CubeSat

0 (default) | degrees between 0 and 360

Angle between the periapsis (closest point of orbit to Earth) and the current position of CubeSat, specified between 0 and 360 deg.

Programmatic Use

Block Parameter: nu

Type: character vector

Values: scalar

Default: '0'

True longitude [deg] (circular equatorial) — Angle between x-axis of periapsis and position of CubeSat vector

0 (default) | degrees between 0 and 360

Angle between x-axis of periapsis and position of CubeSat vector, specified between 0 and 360 deg.

Programmatic Use

Block Parameter: truelon

Type: character vector

Values: scalar

Default: '0'

Argument of latitude [deg] (circular inclined) — Angle between ascending node and satellite position vector

0 (default) | degrees between 0 and 360

Angle between ascending node and satellite position vector, specified between 0 and 360 deg.

Programmatic Use

Block Parameter: arglat

Type: character vector

Values: scalar

Default: '0'

Longitude of periapsis [deg] (elliptical equatorial) — Angle between x-axis of periapsis and eccentricity vector

0 (default) | degrees between 0 and 360

Angle between the x-axis of the periapsis and the eccentricity vector, specified between 0 and 360 deg.

Programmatic Use

Block Parameter: lonper

Type: character vector

Values: scalar

Default: '0'

ECI position vector [m] — Cartesian position vector

[0 0 0] (default) | vector

Cartesian position vector of satellite in ECI coordinate frame at Start Date.

Programmatic Use

Block Parameter: r_eci

Type: character vector

Values: scalar

Default: '[0 0 0]'

ECI velocity vector [m/s] — Cartesian velocity vector

[0 0 0] (default) | velocity vector

Cartesian velocity vector of satellite in ECI coordinate frame at Start Date.

Programmatic Use

Block Parameter: v_eci

Type: character vector

Values: scalar

Default: '[0 0 0]'

ECEF position vector [m] — Cartesian position vector

[0 0 0] (default) | vector

Cartesian position vector of satellite in ECEF coordinate frame at Start Date.

Programmatic Use

Block Parameter: r_ecef

Type: character vector

Values: scalar

Default: '[0 0 0]'

ECEF velocity vector [m/s] — Cartesian velocity vector

[0 0 0] (default) | velocity vector

Cartesian velocity vector of satellite in ECEF coordinate frame at Start Date.

Programmatic Use

Block Parameter: v_ecef

Type: character vector

Values: scalar

Default: '[0 0 0]'

Geodetic latitude, longitude, altitude [deg, deg, m] — Geodetic latitude and longitude, and altitude

[0 0 0] (default) | velocity vector

Geodetic latitude and longitude, in deg, and altitude above WGS84 ellipsoid, in m.

Programmatic Use

Block Parameter: lla

Type: character vector

Values: scalar

Default: '[0 0 0]'

NED velocity vector [m/s] — Body velocity

[0 0 0] (default) | velocity vector

Body velocity with respect to Earth-centered Earth-fixed (ECEF), expressed in the north-east-down (NED) coordinate frame, specified as a vector, in m/s.

Programmatic Use

Block Parameter: v_ned

Type: character vector

Values: scalar

Default: '[0 0 0]'

CubeSat Attitude

Initial Euler angles (roll, pitch, yaw) [deg] — Initial Euler rotation angles

[0 0 0] (default) | vector | degrees

Initial Euler rotation angles (roll, pitch, yaw) between Body and NED coordinate frames, specified in degrees.

Programmatic Use

Block Parameter: euler

Type: character vector

Values: scalar

Default: '[0 0 0]'

Initial body angular rates [deg/s] — Initial angular rates

[0 0 -0.05168] (default) | vector

Initial angular rates with respect to NED frame, expressed in Body frame, specified as a vector.

Programmatic Use

Block Parameter: pqr

Type: character vector

Values: scalar

Default: '[0 0 0]'

Pointing mode — CubeSat vehicle pointing mode

Earth (Nadir) Pointing (default) | Sun Tracking | Custom Pointing | Standby (Off)

CubeSat vehicle pointing mode, specified as Earth (Nadir) Pointing, Sun Tracking, or Custom Pointing. The CubeSat vehicle uses the pointing mode for precise attitude control. For no attitude control, select Standby (Off).

Programmatic Use

Block Parameter: pointingMode

Type: character vector

Values: 'Earth (Nadir) Pointing' | 'Sun Tracking' | 'Custom Pointing' | 'Standby (Off)'

Default: 'Earth (Nadir) Pointing'

Primary alignment vector (Body wrt B_CM) — Primary alignment vector

Dialog (default) | Input port

Primary alignment vector, in Body frame, to align with primary constraint vector.

Dependencies

• Selecting Dialog enables a text box in which you specify the primary alignment vector. The default value is [0 0 1].

• Selecting Input port enables the 1^st Alignment_Body input port, at which you specify the primary alignment vector.

Programmatic Use

Block Parameter: firstAlign

Type: character vector

Values: vector

Default: '[0 0 1]'

Programmatic Use

Block Parameter: firstAlignExt

Type: character vector

Values: 'Input port' | 'Dialog'

Default: 'Dialog'

Secondary alignment vector (Body wrt B_CM) — Secondary alignment vector

Dialog (default) | Input port

Secondary alignment vector, in Body frame, to align with secondary constraint vector.

Dependencies

• Selecting Dialog enables a text box in which you specify the secondary alignment vector. The default value is [0 1 0].

• Selecting Input port enables the 2^nd Alignment_Body input port, at which you specify the secondary alignment vector.

Programmatic Use

Block Parameter: secondAlign

Type: character vector

Values: vector

Default: '[0 1 0]'

Programmatic Use

Block Parameter: secondAlignExt

Type: character vector

Values: 'Input port' | 'Dialog'

Default: 'Dialog'

Constraint coordinate system — Constraint coordinate system

ECI Axes (default) | ECEF Axes | NED Axes | Body-Fixed Axes

Constraint coordinate system, specified as ECI Axes, ECEF Axes, NED Axes, or Body-Fixed Axes.

Programmatic Use

Block Parameter: constraintCoord

Type: character vector

Values: 'ECI Axes' | 'ECEF Axes' | 'NED Axes' | 'Body-Fixed Axes'

Default: 'ECI Axes'

Primary constraint vector (wrt B_CM) — Primary constraint vector

Dialog (default) | Input port

Primary constraint vector, in the Body frame, to align with the primary alignment vector.

Dependencies

• This parameter is disabled when Pointing mode is Earth (Nadir) Pointing or Sun Tracking.

• Selecting Dialog enables a text box in which you specify the primary constraint vector. The default value is [1 0 0].

• Selecting Input port enables the 1^st constraint_Body input port, at which you specify the primary constraint vector.

Programmatic Use

Block Parameter: firstRef

Type: character vector

Values: vector

Default: '[1 0 0]'

Programmatic Use

Block Parameter: firstRefExt

Type: character vector

Values: 'Input port' | 'Dialog'

Default: 'Dialog'

Secondary constraint vector (wrt B_CM) — Secondary constraint vector

Dialog (default) | Input port

Secondary constraint vector, in the Body frame, to align with the secondary alignment vector.

Dependencies

• Selecting Dialog enables a text box in which you specify the secondary constraint vector. The default value is [0 0 1].

• Selecting Input port enables the 2^nd constraint_Body input port, at which you specify the secondary constraint vector.

Programmatic Use

Block Parameter: secondRef

Type: character vector

Values: vector

Default: '[0 0 1]'

Programmatic Use

Block Parameter: secondRefExt

Type: character vector

Values: 'Input port' | 'Dialog'

Default: 'Dialog'

Mission Analysis

Analysis run time source — Source of run time for mission analysis live script

Dialog (default) | Model Stop Time

Source of run time for mission analysis live script, specified as:

• Dialog — Defined in Run time parameter.

• Model Stop Time — Defined in model configuration parameter Stop Time.

Programmatic Use

Block Parameter: missionRTSource

Type: character vector

Values: 'Dialog' | 'Model StopTime'

Default: 'Dialog'

Run time [sec] — Run time for mission analysis live script

6*60*60 (default) | scalar

Run time for mission analysis live script, specified as a scalar.

Programmatic Use

Block Parameter: missionRT

Type: character vector

Values: scalar

Default: '6*60*60'

Ground station geodetic latitude, longitude [deg, deg] — Ground station location

[42, -71] (default) | vector

Ground station location, specified as a vector, in geodetic latitude and longitude in deg, deg.

Programmatic Use

Block Parameter: missionGS

Type: character vector

Values: vector

Default: '[42, -71]'

Run TOI analysis — Enable time of interest mission analysis

on (default) | off

Select this check box to enable time of interest analysis in a mission analysis live script.

Programmatic Use

Block Parameter: missionTOICheck

Type: character vector

Values: 'on' | 'off'

Default: 'on'

Time of interest [Julian date] — Time of interest for mission analysis live script

[] (default) | Julian date

Time of interest mission analysis, specified as a Julian date. To use the simulation start date, enter an empty array ([]).

Tip

To calculate the Julian date, use the juliandate function.

Programmatic Use

Block Parameter: missionTOI

Type: character vector

Values: Julian date

Default: '[]'

Camera field-of-view (FOV) half angle (deg) — Half angle of field of view

55 (default) | [] | scalar

Half angle of field of view for nadir on-pointed camera. To exclude from analysis, enter an empty array ([]).

Programmatic Use

Block Parameter: missionEta

Type: character vector

Values: '[]' | scalar

Default: '55'

Live script file name — File name for mission analysis live script report

blank entry (default) | live script file name

File name for mission analysis live script report, generated as a live script. To create a default mission analysis report with the format CubeSatMissionReport_currentdate.mlx, leave the parameter blank. To create a live script of the mission analysis report, click the Create Live Script Report button.

Dependencies

To create the live script with the specified file name, click the Create Live Script Report button. If this parameter is blank, the block creates a live script with a default file name.

Programmatic Use

Block Parameter: missionName

Type: character vector

Values: blank entry | file name

Default: blank entry

Create Live Script Report — Analyze mission and create live script report

button

To analyze mission and create report in live script format, click this button. To create a default mission analysis report with the format CubeSatMissionReport_currentdate.mlx, leave the parameter blank. To create a live script of the mission analysis report, click the Create Live Script Report button.

Dependencies

To create the live script with the file name specified in Live script file name, click the Create Live Script Report button. If Live script file name is blank, the block creates a live script with a default file name.

Alternative Configurations

Cubesat Vehicle Sun Tracking — Model CubeSat vehicle with primary alignment vector points toward the Sun

The Cubesat Vehicle Sun Tracking block models CubeSat vehicles with primary alignment vector points toward the Sun. To enable this block, set Pointing mode to Sun Tracking.

Libraries:
Aerospace Blockset / Spacecraft / CubeSat Vehicles

Cubesat Vehicle Custom Pointing — Model CubeSat vehicle with custom alignment and constraint vectors

The Cubesat Vehicle Custom Pointing block models CubeSat vehicles with custom alignment and constraint vectors. To enable this block, set Pointing mode to Custom Pointing.

Libraries:
Aerospace Blockset / Spacecraft / CubeSat Vehicles

References

[1] Wertz, James R, David F. Everett, and Jeffery J. Puschell. Space Mission Engineering: The New Smad. Hawthorne, CA: Microcosm Press, 2011. Print.

Version History

Introduced in R2019a

R2021a: CubeSat Vehicle now propagates in the ECI coordinate frame

The CubeSat Vehicle now propagates in the ECI coordinate frame using Earth orientation parameters data from the aeroiersdata.mat file. Results differ from previous releases, but are more accurate than with previous versions of the block.