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Space & Satellite

Spacecraft and Satellites Mass Properties Measurement

SatelliteRaptor Scientific manufactures test and ground support equipment for spacecraft design, production, and testing. Our instruments are used across the globe to measure manned spacecraft and satellites of all sizes. Our customers include NASA, Jet Propulsion Laboratory, Thales Alenia Space (Italy), JAXA (Japan), NSPO (Taiwan), KARI (South Korea), and Turkish Aerospace Industries. Here are some of the programs we’ve supported in recent years.





NASA Orion Multipurpose Crew Vehicle Boeing CST-100 Starliner

Large Satellites and Manned Spacecraft

Raptor Scientific manufactures the only instruments in the world that can measure all mass properties in one setup. These combined instruments reduce handling of the spacecraft and the risks associated with it. Two types of instruments answer the particular needs of the space industry:

  • Our KSR instruments measure center of gravity and moment of inertia. This is the most popular instrument for spacecraft testing centers worldwide.
  • Our POI instruments measure center of gravity, moment of inertia, product of inertia, and dynamic unbalance. These are used for certain categories of spacecraft that require spin balancing or accurate knowledge of product of inertia.
Boeing CST-100 Starliner

Small Satellites

Knowledge of the mass properties of a small satellite is essential to understanding its flight dynamics and adjusting its attitude control loop. Space Electronics has developed the following suite of mass properties instruments:

  • Our SE90168 series of instruments measure the center of gravity location of CubeSats and small satellites. These instruments come in several sizes for testing of payloads weighing from 500 grams (1 lb) to over 100 kg. Accuracy in the range of ± 1 mm is exactly what is needed for the small satellite community.
  • Our XR series moment of inertia instruments measure moment of inertia. Three sizes are available to cover 1U CubeSats through 100 kg spacecraft. Accuracy is in the order of 0.25% of measured quantity, which is compatible with the generic accuracy of 1% for the industry.
  • The FBD series are new spin balance instruments that measure product of inertia and perform dynamic balancing. Center of gravity can also be measured in a dynamic fashion on these instruments.

All of these instruments are intrinsically compatible with cleanroom requirements. They do not incorporate any hydraulic circuitry that could damage flight hardware.

Fixturing for Mass Properties Testing


Fixturing for Mass Properties Testing combo image

Fixturing is an essential part of accurate mass properties measurement. Space Electronics manufactures all fixtures necessary for mass properties testing:

  • Our vertical adapters are used to position the spacecraft in a vertical orientation. This allows measurement of center of gravity in two axes (CGx and CGy) and of moment of inertia around a vertical axis (Izz).
  • L fixtures are used for holding spacecraft in a horizontal orientation, for measurement of center of gravity height (CGz) and lateral moments of inertia (Ixx and Iyy). Our L fixtures also allow rotation of the spacecraft in finer increments to measure product of inertia in the XY plane (Ixy).
  • A 3-axis positioner can also be used. This is an elaborate fixture that holds the spacecraft at multiple angles to measure all mass properties (CG in 3 axes, MOI in 3 axes, and POI in 3 planes). It allows calculation of product of inertia based on moment of inertia measurement, so the entire inertia tensor can be derived with the use of a KSR instrument. The spacecraft positioner also minimizes handling of the spacecraft. The spacecraft is mounted in a vertical orientation; the positioner rotates the spacecraft to the various measurement positions and brings the spacecraft back to vertical for easy dismounting.

Mechanical Ground Support Equipment

We manufactures ground support equipment for spacecraft manufacturing and testing. These include:

  • Vacuum-compatible L brackets for holding a spacecraft in a thermal vacuum chamber (TVAC testing)
  • Positioners for Compact Antenna Test Range (CATR)
  • Multi-Purpose Trolleys (MPT) for rotating a spacecraft from vertical to horizontal position
  • Support trolley for acoustic chamber, with resonance frequency between 2 and 4 Hz
  • Handling bars for handling objects with variable center of gravity location with a crane. These are used for example to handle both empty L fixtures and the combination of L fixture and satellite.

Attitude Control System Testing

Raptor Scientific manufactures hemispherical and spherical air bearings that are used as frictionless test platforms to test attitude control systems.



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