Project Rahu

Eclipse Observation Balloons

On August 21, 2017 we launched four camera-equipped weather balloons from NW of Madras, OR into the path of the total solar eclipse. Our goal, besides experiencing the eclipse on the ground, was to see what the complete umbra looks like from above most of the atmosphere, something only a handful of photographs had been taken of prior to this eclipse.

After months of prep, we released our balloons at 7:28 (Rahu I), 7:34 (Rahu IV), 7:40 (Rahu II), and 7:48 (Rahu III). We recovered equipment from all four balloons, though trackers from Rahu II became separated from the rest of the payload, so we lost those four cameras. As we sort through the hours of video footage and thousands of still images, we will continue to update this page over the coming days and weeks.

View of the shadow of the eclipse approaching from the Oregon coast from Rahu IV at 83,000 feet at 10:16am.
Rahu I at 86,000 feet is just visible as a tiny speck of white over the shadow.

Umbra engulfing Mt. Jefferson at 10:18am from Rahu IV.

Mt. Jefferson completely in the shadow at 10:18 from Rahu I.

The eclipse completely filling the space between the Three Sisters and Mt. Hood.
Mt. Jefferson is in complete darkness at 10:19.

View of the shadow of the eclipse receding from Rahu I at 90,000 feet at 10:23am.
Rahu IV at 87,000 feet is clearly visible as a white dot in front of the shadow.

Preliminary flight stats

Rahu 0 (Test)

Rahu I

Rahu II

Rahu III

Rahu IV

Release time

11:37 Aug 3

7:28 Aug 21

7:40 Aug 21

7:48 Aug 21

7:34 Aug 21

Burst time






Landing time






Ascent time

3 hr 1 min

3 hr 32 min

3 hr 36 min

3 hr 32 min

3 hr 23 min

Descent time

38 min

40 min

28 min

21 min

47 min

Total flight time

3 hr 39 min

4 hr 12 min

4 hr 4 min

3 hr 53 min

4 hr 10 min


54 mi

30.5 mi

28.4 mi

26.8 mi

28.4 mi

Initial ascent rate

613 ft/min

461 ft/min

379 ft/min

481 ft/min

470 ft/min

Final ascent rate

544 ft/min

238 ft/min

352 ft/min

325 ft/min

512 ft/min

Max descent rate

4521 ft/min

7115 ft/min

4306 ft/min*

7339 ft/min

6476 ft/min

Landing speed

1185 ft/min
13.5 mph

1319 ft/min
15 mph

2696 ft/min
30 mph

2629 ft/min
30 mph

1283 ft/min

Altitude during eclipse


88781 feet

77713 feet

75222 feet

85699 feet

Max altitude

103045 feet

107707 feet

105581 feet

105981 feet

105354 feet

Lowest internal temp

14ºC @ 57000ft

-30ºC @ 92000ft

-26ºC @ 81000ft

-28ºC @ 78500ft

-32ºC @ 88000ft

Lowest pressure

1502 Pa

836 Pa

995 Pa

1102 Pa

1154 Pa


*Average descent rate from burst to first transmission received 15 minutes after burst.

Project Details



David talks about the role of failure in Project Rahu:

Craig talks about the role of ambition and preparation in Project Rahu:


The 720g payloads are carried by 1000g Kaymont balloons.

Helium and balloon inflation





The primary payloads were Xiaomi Yi cameras for stills and 808 keychain cameras for video, both with supplemental batteries.


For weight and low temperature performance, all components were powered by either Energizer Lithium AA batteries (tracking) or rechargeable LiPo batteries (cameras.)


Our primary tracking was done via Tracksoar APRS transmitters, designed by Mike Bales. The balloons transmitted on 144.39 as KJ6DYP-11, KJ6DYP-14, KJ6DYP-12, and KJ6DYP-13.

Backup satellite tracking was by Spot Trace. While the Spots ultimately did give us landing locations, the devices do not transmit continuously and went to sleep after being carried to the launch area the night before. We were disconcerted to find that they were not transmitting immediately after launch. We later learned that the release and flight were not enough motion to wake them.

We did not expect them to report locations above 60,000 feet, but they did wake up when they started falling and began transmitting once they fell below 60,000 feet. Spot has provided a firmware update that increases the sensitivity to motion, though we have not yet tested it.

You can see the tracks of all of our balloons online via APRS.

flight paths

Enclosures and Chassis


Launch site

We camped and released our balloons on public land in the Crooked River National Grassland.

map of shadow and launch site


flight photo of other balloons
From its lower altitude at the back of the pack, the Yi camera on Rahu III was able to capture all three of our other balloons, as well as two other eclipse-day balloons.

Map showing relative locations of balloons as they became large enough to see each other clearly. Red circles are burst points. Colored spots are approximate locations of balloons when others burst.

Video from Rahu III shows the balloon closest to Rahu II, sent up by TJ Eaton, KI7CUX, rising from below and suddenly blinking out above Rahu II, presumably when it burst. Unfortunately, the Rahu II cameras were not recovered. Rahu IV burst immediately after the image above was taken.

Rahu III closed to within 1.2 miles Rahu II, and took its final shots of Rahu II before the camera failed about a minute before Rahu II burst.

Rahu 2 from Rahu 3

Links we found useful

Ikaros Home Page