since 1996; SNO began operation in the summer of 1999; and Borexino and Kamland are under construction.

The second-generation microlensing experiments currently being started (OGLE II and Super MACHOs) should have the photometric and statistical accuracy to break the degeneracy among mass, distance, and velocity of the lensing objects. The Space Interferometry Mission (SIM) should also pin down the distance of the lenses.

The Axion experiment has published preliminary limits and will reach the required sensitivity for one generic type of axion between 10⁻⁶ and 10⁻⁵ eV/c². By pushing the sensitivity with SQUID amplifiers and by operating at 100 mK, an upgraded Axion experiment would cover all the present axion models in this mass range, which is one-third of the 10⁻⁶ to 10⁻³ eV/c² range allowed by astrophysical constraints.

The Cryogenic Dark Matter Search II promises to be the most sensitive WIMP experiment at the beginning of the 2000 decade. It should improve current sensitivities by two orders of magnitude and reach well into the supersymmetric region.

AMANDA II will increase the sensitivity of the search for neutrinos from WIMP annihilation and AMS will search for an excess of antiprotons and positrons in the cosmic rays.

The panel was able to identify several key challenges that are ripe for progress at this time:

• To detect gravitational radiation from interacting massive objects, including massive black holes;

• To understand the origin of gamma rays of very high energy from sources such as AGN and SNRs;

• To identify positively the sources of galactic cosmic rays and to measure the output of these cosmic accelerators;

• To identify the nature and distribution of the bulk of the matter in the universe;

• To understand the origin of the highest-energy particles in nature;

Front Matter (R1-R26)

Executive Summary (1-16)

1 Report of the Panel on High-Energy Astrophysics from Space (17-64)

2 Report of the Panel on Optical and Infrared Astronomy from the Ground (65-122)

3 Report of the Panel on Particle, Nuclear, and Gravitational-Wave Astrophysics (123-166)

4 Report of the Panel on Radio and Submillimeter-Wave Astronomy (167-220)

5 Report of the Panel on Solar Astronomy (221-274)

6 Report of the Panel on Theory, Computation, and Data Exploration (275-326)

7 Report of the Panel on Ultraviolet, Optical, and Infrared Astronomy from Space (327-374)