National Aeronautics and Space Administration

WASP is a NASA provided support system, developed at NASA’s Wallops Flight Facility (WFF), which points science instruments 

on balloon gondolas at targets with arc-second accuracy and stability. WASP can support a variety of science-provided instruments 

and sensors, and multiple science disciplines, to meet specific mission performance requirements. Pointed masses over 600 kilograms 

and instrument dimensions over one meter in diameter and eight meters in length can be supported. Major components of WASP 

are reusable which reduces the overall costs to the BPO and to users. Collaborative design, analysis, integration and flight support 

services are available from WFF for proposers who want to use WASP. 

Since its inaugural flight in 2011, the WASP system has been used to provide fine pointing of five unique scientific instruments during 

the conduct of eight balloon flights. WASP has demonstrated positional stability at sub-arc-second levels during flight. In September 

of 2013, WASP supported its first pointed science instrument, the HyperSpectral Imager for Climate Science (HySICS), provided 

by the Laboratory for Atmospheric and Space Physics (LASP), which is an institute at the University of Colorado at Boulder (CU).

www.nasa.gov

Wallops Arc Second Pointer (WASP)

The WASP system points an instrument (modeled during TF1 by a 24-ft 1500-lb steel beam) using a gondola mounted pitch/yaw articulated gimbal. The range of motion of the yaw-gimbal is purposely minimized to reduce kinematic coupling during fine pointing. Thus, the 

gondola itself is suspended beneath a standard NASA Rotator to provide large angle azimuth targeting and coarse azimuth stabilization. 

Sub-arc-second pointing is enabled by the design of the WASP gimbal hubs. A pair of hubs on opposing sides of the gimbal is used to 

establish each articulated axis of rotation. Each hub uses high-precision angular contact bearings to float the rotor side and stator side of 

the hub on a central shaft. The central shaft in each hub is constantly rotated by a small diameter torque motor to eliminate static friction. 

A large-diameter brushless DC torque motor is used to provide the torque for each control axis. The current in the three electrical phases in each of the control motors is commutated in software and set using power Op-Amps in a motor interface circuit. 

Instrument attitude is computed by integrating incremental angles (delta-Theta) output from a LN251 system. While the LN251 

is a fully capable GPS/INS navigation system, its use on the WASP system is limited to that of a relatively low-cost, high-quality 

Figure One - Test Flight 1 (TF1) Gondola on Launch Vehicle

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inertial-rate-unit. Control torques are computed using a modified Proportional-Integral-Derivative control law in each axis. During the TF1 WASP 

demonstrated the ability to inertial pointing with sub-arc-second stability. 

After the initial test flight of WASP in 2011, a number of system modifications and improvements were made that included: incorporating a Star 

Tracker into the control system loop, changing the mock telescope from a 24 

foot steel tube to a 16 foot tube with less inertia, moving the avionics deck 

from the outer frame to the mock telescope, and adding angular positional 

encoders to the Resolver Hubs.

The third and fourth flights of WASP, which occurred in the fall of 2013 

and 2014, included the HySICS science instrument provided by LASP, and 

successfully completed scan maneuvers of the sun and observations of 

the earth, moon and earth limb. This flight successfully tested several new 

WASP system enhancements, and demonstrated WASP’s ability to be integrated with science and provide flight support. 

After multiple successful test flights, in 2016 WASP supported the first science support mission with X-Calibur 

from Fort Sumner, New Mexico and in 2018 supported 

the second flight with X-Calibur from McMurdo, Antarctica. X-Calibur, provided by Washington University at St. 

Louis (WUSTL), is a Hard X-Ray Polarimetry Telescope 

operating in the 20–60 keV energy range that observes 

mass accreting black holes and neutron stars. The X-Calibur missions introduced additional WASP enhancements 

which included a NASA Wallops developed Star Tracker 

with an in-flight alignment process and long duration autonomous operations.

During the 2016 WASP flight, the balloon carried the approximately 4,000lb gondola/telescope structure to over 

120,000 feet altitude. WASP was successful at pointing at 

multiple targets including: Crab Nebula, Scorpius X-1, 

Cygnus X-1, and GRS1915+105. Figure three depicts 

Figure Two – WASP HySICS Integrated Gondola

Figure Three - New Mexico WASP/X-Calibur 

Gondola Figure Four - Tracking Error while on Cygnus X1

Figure Five – Antarctica WASP/X-Calibur Gondola

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In the fall of 2019 at Fort Sumner New Mexico, WASP supported two science instruments launches, the Balloon-Borne Investigation of Temperature and Speed of Electrons (BITSE) provided by Goddard Space Flight Center and the Planetary Imaging Concept Testbed Using a Recoverable Experiment Coronagraph (PICTURE-C) provided by University of Massachusetts, 

Lowell.

BITSE was a technology demonstration project. The long term scientific goal enabled by BITSE will be to understand the 

physical conditions in the solar wind acceleration region (3-10 solar radii from the Sun center). The BITSE experiment was 

aimed to validate the technology and performance of a new type of coronagraph to simultaneously measure electron density, 

velocity, and temperature. During the flight, WASP held track on the sun exhibiting the best performance seen on a WASP 

flight to date. The pitch and yaw pointing error RMS varied between 0.15 - 0.20 arc seconds throughout the science pointing 

window. During this time, the science team reported they captured over 17,000 images of the sun with their instrument.

Figure Seven – WASP/BITSE during 

Compatibility Testing

Figure Eight - BITSE Pointing Performance

Figure Six – Raw controller errors during 1st observation GC301-2 

(includes offset pointing)

the New Mexico WASP/X-Calibur design 

configuration.

For the second X-Calibur flight out of Antarctica, the primary science requirement levied 

on WASP was to hold the X-ray mirror axis 

to within 30 arc seconds of the target source 

during each observation. During the flight, 

WASP maneuvered to and acquired multiple 

X-ray sources and provided pointing stability between 1.0 - 3.6 arc seconds while on the 

source. WASP pointing was spent primarily 

on two targets: GX 301-2 and Vela X-1. The 

targets were complementary in that there were 

no times when both sources violated a lower 

or upper look elevation constraint.

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For more information on WASP, please contact the NASA Project Manager at WFF, Mr. Edward Udinski at edward.p.udinski@nasa.gov

NP-2022-9-855-WFF

PICTURE- C took the next steps along the road to 

characterizing Earthlike planets, in Earthlike orbits, 

orbiting Sunlike stars. It demonstrated with a high altitude balloon based clear aperture telescope with Low 

Order Wavefront Control (LOWC), provided a flight 

demonstration of a high performance Vector Vortex 

Coronagraph (VVC), and raised the TRL of an integral field detector, the Microwave Kinetic Inductance 

Detector (MKID). During daytime and nighttime target pointing operations, the WASP system was utilized 

to maneuver to, acquire, and station-keep on 4 science 

targets and 4 calibration targets. During target station 

keeping operations, WASP consistently yielded subarc second pointing performance with pointing RMS 

values that varied between 0.15” and 0.8” depending 

upon the controller gain settings utilized. PICTURE-C 

continued its efforts during a fall 2022 flight from Fort 

Sumner New Mexico with another successful flight. 

While analysis of the flight data is still ongoing, preliminary results reveal what looks like the most stable 

pointing performance of the WASP system to date.

WASP has demonstrated excellent performance during all flights 

and is available for science groups to propose as a solution to their 

fine-pointing needs. Proposals may include WFF-provided collaborative design, simulation, analysis, integration, and field support. 

Figure Nine- PICTURE C Pointing Calibration

Figure 10 - PICTURE C Pointing Performance

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