ALTAIR: The Balloon-Borne Atmospheric Calibrator

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ALTAIR is a balloon-borne optical calibration source used to calibrate the next generation of supernova surveys for probing the nature of the dark energy. The project is a collaboration among colleagues at Harvard University, the University of Victoria, and Dartmouth College. The Dartmouth component has responsibility for vehicle development, telemetry, ground tracking, and flight operations.

Colleagues at the University of Victoria maintain a project website at

Project ALTAIR

31May16    A15B Test Run Completed. During testing over the winter, the mainboard of the LX200 telescope failed. We obtained a new front panel module from Meade and installed it in the telescope, replacing the older version. Indoor tests indicated that the new system was working correctly. Test Tun 15B was an outdoor test to verify that a star alignment could be obtained and that the telescope would point.

We took the telescope to the roof of Wilder and attempted several star alignments. For each attempt, it was not at all clear which star the telescope was attempting to align to, and subsequent pointing (to Jupiter, typically) was off by several degrees. We then performed a "drive training" procedure, and the next alignment seemed to work. A subsequent alignment then failed again.

Back indoors, the telescope failed to complete a star alignment, the operating system crashing at specific steps in the process.

17Nov15    A15A Test Run Completed. In order to track down some of the gremlins that plagued A15, we set up the telescope on the roof of Wilder to learn to use the focal reducer, experiment with star alignment and tracking accuracy, capture some calibration images, and perform the "drive training" procedure to improve pointing accuracy. We completed these tasks, getting some nice images.

27Oct15    A15 Recovered. The gondola was recovered intact using the line launcher to pull it down from the tree. Although a very small amount of water had gotten into the enclosure, all systems functioned normally on test after drying out.

24Oct15    A15 Flies. ALTAIR 15 Launched from Theford Academy at 0451, Saturday 24 October. Winds were less strong than predicted, so cutdown was delayed until 8,768 meters. The science protocol was run largely according to the flight plan during climb. After cutdown, the parafoil did not deploy fully, so the descent was a spiral to a landing on the east side of Goose Pond. Both SPOT and the RF beacon gave good landing location fixes, so the gondola was located easily at the top of a large dead birch.

23Oct15    A15 Ready to Fly. We intend to fly A15 on Saturday morning, launching from Thetford at 0430 EDT. The flight plan calls for cutdown at 7,000 m with glide to landing at Robert Frost. The science payload is the diffusive source.

6Aug15    A14 Recovered. We returned to the landing site with an aroborist's line launcher and were able to put a line through the rigging and pull the vehicle down from the tree. The gondola itself is undamaged, but the parafoil was essentially destroyed in the process.

29Jul15    A14 Flies. Despite some questionable weather and some inexperienced crew, we decided to launch at 0400 Wednesday from Thetford Academy, with the goal of a climb to 4000 m, and a glide to landing at Robert Frost Lane. In addition to testing the new parafoil deployment system and gaining experience with flying the parafoil, a major goal was to obtain quantitative imagery of the new diffusive source. We got bit of a late start, so launch was well into twilight. The telescope tracked perfectly, but the sky was too bright to obtain any imagery. We cut down at nearly 4500 m and the parafoil deployed correctly For some reason the vehicle entered Landed mode while still in flight so steering was impossible. Telemetry was lost as the vehicle passed behind Moose Mountain. Amazingly, the recovery beacon was still loud and clear from Etna after landing. The SPOT corroborated the beacon.

With coordinates in hand, we located the vehicle just east of Goose Pond at 43.69246,-72.08444 and about fifty feet up an end-of-life spruce. We declined to climb the tree, so did not recover the vehicle. More information on the Flights page.

28Jul15    A14 Punch List Complete. All items on the A14 Critical Items list have been addressed. Final integration and packing were completed late afternoon.

26Jul15    Source Calibration Complete. Karun has completed an extensive calibration process demonstrating that the LED diffusive source is azimuthally symmetric, achromatic, and nearly Lambertian. He is still working on detailed analysis.

20May15    Diffusive Source Complete. The new LED-based diffusive source is complete and integrated into the gondola. We have begun calibration testing. The source is nearly Lambertian with an on-axis radiance of 32 mW/sr in the green channel.

17May15    Drop Tests Successful. In order to alleviate some complexity and unreliability in the parafoild deployment system, we have designed and tested a newer method that eliminates the "clip" in favor of draping the parafoil over the release cord. This system tested reasonably well in drop tests from the roof of Wilder, but we wanted to test it from a larger height. We've now completed two sets of tethered flights and have worked out the bugs and have what we believe is a reliable deployment mechanism.

22Aug14    ALTAIR 14 Buildup Complete. Over the past eight weeks we have been working on completing a design iteration and the fabrication of the next gondola. (See the Planning page for details.) The new gondola includes an improved cutdown system, all new electronics incorporating lessons learned from previous flights and tests, and various improvements to the gondola structure. The new design is still aimed at carrying the laser-diode-integrating-sphere light source, but will also accommodate the diffusion-based source we have been contemplating.

We have tested the telemetry system from Mt Ascutney to Etna, with good reliability both using the yagi antenna and the omni-directional duckie on the ground station. We conducted these tests from two locations in Etna--Sunset Rock Road and Robert Frost Lane. In addition, we tested the RF Beacon as a car carried the gondola from Robert Frost to the pond on Dogford Road. The beacon was readable throughout the trip.

28Jun14    ALTAIR 13 Flies. A13 was intended as a moderate-altitude flight to test flight systems, gain experience with the new navigation system and obtain imagery from the new science protocol. The flight was planned from Thetford Academy to an altitude of 6,500 meters, and then to a landing at Robert Frost, where the science station was located. Unfortunately, telemetry failed within a minute after release. The science station received only a short burst of data after the vehicle climbed into view. The vehicle flew to burst and landed somewhere in south-central New Hampshire. We observed the burst visually in binoculars from the science station. After making an estimate of landing based on known time of flight and forecast winds, we conducted a ground search in the general vicinity of Unity, NH, but heard nothing from the RF Beacon.

23Jun14    ALTAIR 12B. After making some improvements to the software and fabricating a mounting pole that would allow us to raise the gondola about ten feet off the ground, we conducted another ground test from Gile Mt to Robert Frost. Telemetry again failed while using the omni antenna on the gondola, but succeeded with a yagi mounted on the pole. We obtained numerous images using the automated science protocol and the engineering LED light source.

16Jun14    ALTAIR 12A. Since we failed to obtain imagery from A12, we decided to conduct a ground test with the gondola at the summit of Mt Ascutney and the science station at Robert Frost. The test was aborted because we received no telemetry from Ascutney. Evidently multi-path effects overwhelmed the ability of the telemetry radios to cope. After returning from Ascutney, the gondola team carried the unit to Dogford Rd for a shorter range test. The telemetry worked over this range but was somewhat sporadic. Again, the path is through some trees.

18May14    ALTAIR 12 Flies. After a long winter of developing new systems and procedures, A12 was a short hop from Garipay to Robert Frost intended to validate these new systems. We especially wanted to test the new RF Beacon, Nav Interface, and automated science protocols and camera control. After a successful launch, the vehicle flew to 3500 m, cut down without incident, and began controlled parafoil flight. We maneuvered to the landing field, but steering was very touchy and we were unable to turn upwind for landing. The vehicle landed in the Bluberry Hill area. We received coordinates from the new RF Beacon at a range of 3 km, and also received telemetry data from the ground. The vehicle was found by residents in the area and returned to campus. Be sure to check out the on-board video on the Flights page.

22Oct13    ALTAIR 11 Recovered. An arborist from Chippers, a local landscaping company, climbed the tree and retrieved the vehicle largely unharmed. Back in the lab, the only damage was a broken shroud line, which we easily replaced.

12Oct13    ALTAIR 11 Flies. We launched from Thetford Academy before dawn with the objective of getting imagery from a science station at Robert Frost Lane and steering the parafoil to a landing there. We obtained imagery, but at about 4,000 m the vehicle began losing altitude. We cut down, but the steering appeared ineffective. The vehicle landed in the top of a very tall tree off Stowell Road in Thetford, VT.

12Aug13    ALTAIR 10 Recovered. After some exciting tree-climbing by Todd, we recovered the vehicle intact from about 60 feet up a maple in the woods of the Morton Farm.

11Aug13    ALTAIR 10 Flies. This flight was a short hop free flight from Garipay to Robert Frost. The main goal was to get imagery with the SBIG camera and LX200 telescope. Tracking worked, but there was enough offset to keep the target outside the field of view of the camera. The parafoil did not deploy properly and consequently did not respond to steering commands. It overshot the recovery zone and descended into the woods on King Hill.

7Aug13    ALTAIR 9 Flies. A free flight from Thompson's to Robert Frost was clouded out, so we did a series of highly successful tethered flights demonstrating the smooth deployment and steerability of the new parafoil.

Pictures and video here.

2Aug13    Justin visits from UVic. Justin has arrived for a 14-day visit which will include flight of A9 and A10.

31Jul13    Buildup of A9 Complete. This version is the "Test Gondola" assembled from parts salvaged from the destroyed A8. The parafoil deployment system uses a friction clip below the spreader bar to hold the foil in a configuration that is conducive to rapid inflation.

30Jul13    Indoor tests of new parafoil. The new rectangular-planform parafoil has arrived. We have performed numerous drop tests in Fairchild Tower refining a reliable deployment system.

30Jun13    ALTAIR 8 Flies. We conducted a set of tethered flights to test the parafoils. Stability is a problem! On one flight with the 2.2-m foil, the vehicle spun into the ground destroying the gondola. This gondola includes a newly redesigned and tested cutdown and steering mechanism that uses a rigid crank connecting rod rather than a string-and-spring arrangement.

20Jun13    Karun visits from UVic. Karun visited for a 12-day visit in which we made progress integrating the prototype source and conducted the A8 tethered parafoil tests.

17Jun13    Max Leaves for Purdue. We say goodbye to our colleague Max Fagin, who leaves for graduate school at Purdue University. All our best wishes to Max as he begins this next great adventure.

16Jun13    ALTAIR 8 nearly complete. The system has been nearly rebuilt with an improved cutdown mechanism that is more positive than before and which completes the entire cycle in 1.2 seconds.

12Jun13    ALTAIR 7A Flies. In order to see the whole process of cutdown and gliding flight we flew the system suspended from a 4-m parafoil rather than a balloon. At Garipay Field we first flew the dummy gondola and allowed it to glide under the 4-m wing. It behaved well. Since the wind was not strong enough to lift the loaded 2.2-m wing, we flew the entire system from the 4-m wing, attaining 56 m AGL. On cutdown, the vehicle entered a right turn as expected, but the turn rapidly tightened into a very fast spiral. The gondola was seriously damaged on impact. Apparently, the cutdown does not recover quickly enough to allow the vehicle to establish steady flight.

11Jun13    Parafoil Drop Tests In order to understand the parafoil steering issue, we performed several drop tests from the roof of Wilder Laboratory. Using the dummy gondola, we were able to achieve gently turning flight both left and right with small adjustments of the control line lengths. We also measured the righting moment and available turn force from the actual gondola using the actual steering mechanism. All appears in order.

9Jun13    ALTAIR 7 Flies. After modifying the cutdown and steering and performing numerous ground tests, we again attempted a short flight from Garipay Field to Robert Frost Lane. Again, the steering seemed largely unresponsive, although in this case the heading stabilized during descent. The descent rate, however, was unaccountably high at about 13 m/s. The vehicle landed in a swamp in Etna, and was easily recovered that morning. It appeared completely undamaged by the flight, despite the rapid descent.

5Jun13    ALTAIR 6 Flies. This flight was largely a test of the new parafoil recovery system. We launched from Garipay Field at Dartmouth and flew the balloon to an altitude of 2600 m with the hope of flying the gondola to a landing at Robert Frost Lane in Etna. All launch and in-flight procedures went very smoothly, with cutdown as planned, but steering seemed essentially unresponsive on descent. The vehicle landed on Signal Hill, just off Stevens Road. We recovered the gondola intact that afternoon after another tree-climbing epic.

4Jun13    ALTAIR 6 Ready for flight. Over the winter we have completed a largely new design of both the gondola mechanics and all electronic systems. The science payload includes the four new high-power laser diode modules, a new optical fiber combiner, and the new lightweight integrating sphere. This new vehicle replaces the old conical recovery parachute with a steerable 2.2 meter parafoil. The idea is that, after cutdown, we will be able to steer the vehicle to a landing at (or at least near) a convenient landing site. Perhaps we've climbed our last tree.

11Dec12    ALTAIR 5A "Flies." We completed a series of optical path tests from Gile Mt to Etna, capturing imagery of the LED beacon, direct illumination from blue and green laser diode modules, and the integrating sphere excited by the blue and green laser diode modules.

5Dec12    ALTAIR 5A Test Stand Complete. While waiting for good flying weather, we have mounted the payload on a test stand that will allow a ground test from the firetower on Gile Mountain to Robert Frost Lane in Etna. This arrangement will allow us to test and refine use of the LX200 system and LD source without all the operational overhead of a balloon flight.

30Nov12    ALTAIR 6 Buildup Complete. ALTAIR 6 is packed and ready to fly. We await appropriate weather. The main mission goal is to test tracking of the LX200 telescope with the laser diode source. The LX200 system has been ground tested including image capture with the SBIG camera. We plan to deploy three ground stations. Launch will include the LT-6 and 50-mm tracking and imagery telescopes. The science station, with the LX200 and SBIG camera, will be located on the roof of Wilder Lab. Recovery will be stationed on Mt Cardigan as usual.

24Oct12    ALTAIR 5 Recovered. A ground search party found the gondola very near the landing site extrapolated from nav data. An analysis of the gondola indicates that the ELT failed due to broken antenna connection. All other systems are in order.

18Oct12    ALTAIR 5 Aerial Search. An aerial search of the A5 touchdown zone failed to find the vehicle.

13Oct12    ALTAIR 5 Flown. ALTAIR 5 launched just after dawn from the campus of Thetford Academy on 13 Oct. After a getting a good star alignment before dawn, the flight proceeded largely as planned, with a flight path that carried the vehicle past Mt Cardigan nearly to Alexandria. Because of a focus error with the imagery telescope, no imagery was obtained, but the vehicle was tracked visually with the LT-6 Telescope. Recovery received telemetry data to within 200 meters of the surface. A recovery team sent to the touchdown area was unable to receive an ELT signal.

31Aug12    ALTAIR 4 Recovered. The gondola was recovered from a tree on the east slope of Mt Cardigan very near the site extrapolated from trajectory data. All systems were found in good condition.

23Aug12    ALTAIR 4 Flown. ALTAIR 4 launched in the very early morning of 23 August from Taftsville, VT. The flight lasted 59 minutes and the flightpath carried the vehicle over Hanover to a landing on the east slopes of Mt Cardigan. Except for difficulties in securing a star alignnment for the tracking telescope, flight operations went smoothly. Nevertheless, the optical signal was lost a few minutes into the flight, so no imagery was obtained.

7Aug12    ALTAIR 4 Buildup Complete. The prototype optical payload from UVic is integrated and tested and the vehicle is ready to fly.

19Jul12    ALTAIR 3 Recovered. We recovered ALTAIR3 from a tree on the west slope of Spruce Ridge south of Groton, NH. The gondola was intact and in good condition. There was no balloon debris attached and all the rigging appeared normal.

14Jul12    ALTAIR 3 Launched. ALTAIR3 launched from Garipay field at 0021 EDT, flew to 20km and landed about 6 km north of Mt Cardigan. The vehicle has been found but not yet recovered.

1Jul12    Drop Test Successful. After a redesign of the cutdown system, rigging, and parachute deployment system we conducted a series of drop tests both indoors and from tethered balloons. In early tests, the parachute deployment system proved problematic but after a second redesign, the new system has shown itself to be robust against tangling and reliable in deployment of the parachute.

28Apr12    ALTAIR 2 Recovered. The vehicle was recovered from a point about 70 feet above the 45th parallel on. The cutdown worked correctly, but rigging tangled and prevented complete separation from the balloon. Apparently the shock of cutdown burst the balloon and the entire vehicle descended.

11Apr12    ALTAIR 2 Launched. ALTAIR 2 launched in the early morning of 11Apr from Mt Washington Regional Airport. The flight path took it south over the high peaks and above the White Mountain National Forest. All flight and telemetry systems worked correctly and the internal temperature was maintained within the expected range. The entire operation was conducted with minimal personnel as a test of a streamlined launch procedure. The tracking system worked correctly, with the vehicle appearing visually in the LT-6 with 25 mm ocular. The cutdown appeared to work correctly, but the descent rate was greater than expected, indicating a failure of the parachute to deploy correctly. We had good GPS data close to the ground on descent, and the ELT worked correctly, so the recovery team was able to locate the vehicle the same day. Because of the rapid descent, the the vehicle did not travel downrange as far as planned and landed in the WMNF somewhat farther north than expected.

24Mar12    Buildup of ALTAIR2 Complete. The weather over the winter never permitted a launch of the improved version of ALTAIR1, so we concentrated on a new basic design that includes a mechanical cutdown and improved mechanical design for weight reduction and much improved thermal performance. Buildup and cold testing are now complete and the new ALTAIR2 gondola is ready to fly.
19Sep11    We successfully recovered ALTAIR1 from dense forest on Mt Tecumseh, just south of the Waterville Valley Ski area.

2Sep11    ALTAIR 1 launched successfully from Mt Washington Regional Airport, Whitefield, NH at 1107 EDT. Telemetry worked well, but the beacon failed and we have not yet recovered the gondola. More pictures on the Images page, and flight data is on the Data page. Summary document:   ALTAIR1Debrief.pdf
Aug11   We're making progress towards a first launch scheduled for 1-2 Sep in coordination with Dartmouth's Greencube project.

28Jul10    Greencube 3 launched successfully. Two balloons--Fred and Henry--launched at night from Mt Washington Regional Airport in Whitefield, NH. They were recovered the following morning. Fred carried a bank of high-brightness LEDs flashing twice per second. These LED sources were successfully tracked from the ground using telemetered GPS data. See here for video.

19May10    Mak500 experiments. See Images.

Dartmouth Balloon Observatory Site
Harvard Flatscreen Calibrator Project Site